Best practice opportunities for DOTs renewable energy in the rights-of-way

Renewable energy generation in the DOT ROW, 2017

The FHWA and U.S. DOT/Volpe Center (2010) have estimated that the National Highway System encompasses approximately 5 million acres of land and nearly 550,000 lane miles.  With over 8 million lane miles of public roadways under state DOT supervision, the properties that DOTs manage are presumably locations with the potential to generate significant amounts of renewable energy (e.g., via sun, wind, arable land, etc.).

Best practice opportunities for DOTs are:

• Consider revising State Utility Accommodation Policies to include renewable energy.
• Identify State statutory or regulatory constraints that preclude renewable resource development.  Address so that they foster such development.
• Identify appropriate renewable energy technologies and potential sites through a statewide or regional feasibility study.
• Review Long Range Transportation Plans (LRTP) to identify potential siting conflicts. Consider developing guidelines for how renewable energy and alternative fuel facility projects can be considered during the statewide transportation planning process and how their performance can be assessed.
• Develop an internal interdisciplinary team to address the unique issues renewable energy projects in the ROW present.
• Create partnerships with external stakeholders.
• Develop comprehensive value-based selection criteria (in addition to criteria based on technical characteristics and price) for renewable energy and alternative fuel facility projects in highway ROW.

FHWA can further help states achieve desired outcomes by removing existing obstacles and providing incentives to encourage DOTs and energy developers to produce alternative power along the highway ROW. Opportunities and potential next steps for FHWA are:

• Clarify its endorsement of using highway ROW to accommodate renewable energy technologies and alternative fuel facilities.
• Consider the use of pilot projects to identify any needed revisions or policies that restrict a DOT’s ability to construct and operate renewable energy technologies and alternative fuel facilities in highway ROW.
• Discuss potential patent issues for renewable energy projects in highway ROW with the American Association of State Highway and Transportation Officials (AASHTO) and other relevant partners.
• Coordinate early involvement with the U.S. Department of Energy to facilitate the development of renewable energy projects in the highway ROW.
• Evaluate the benefits of comprehensive value-based selection criteria for renewable energy and alternative fuel facility projects in highway ROW.
• Analyze effective DOT practices in administering ROW access on routes controlled under the Highway Beautification Program.
• Consider the benefits of sponsoring research to evaluate rest areas, excess lands, and other transportation ROW for renewable energy generation.
• Help build a community of practice that develops and provides training and technical assistance to ROW practitioners and other stakeholders on accommodating alternative energy technologies and alternative fuel facilities.

Case studies included:

Renewable Energy in the ROW Feasibility Research: Colorado DOT Ohio DOT Texas DOT Massachusetts DOT

Solar Energy Projects: Oregon DOT’s Solar Highway Projects California’s Proposed Highway 50 Solar Energy Projects Carver, Massachusetts’ Proposed Route 44 Solar Energy Project Ohio DOT’s Veterans’ Glass City Skyway Bridge Solar Array Project Wind Energy Projects Massachusetts DOT’s Proposed Wind Energy Project along the Massachusetts Turnpike Ohio DOT’s Wind Turbine Project

Bioenergy Projects: Utah DOT’s and Utah State University’s Freeways to Fuel Pilot Project North Carolina DOT’s Bioenergy Pilot Project

Electric Vehicle Charging Stations: Florida Turnpike Enterprise

2017 Peer Exchange

Regulatory Environment

Rosemary Jones of the FHWA Office of Real Estate Services presented on Federal regulatory requirements that guide alternative uses of the highway ROW. For Federal-aid highway projects, ROW property must be devoted exclusively to public highway purposes,¹ but some exceptions exist. Non-highway uses may be approved by FHWA if the use is in the public interest, will not impair the highway, and will not impede the free and safe flow of traffic on the highway.²

The Federal definition for “utility” is broad in scope, and includes facilities that produce, transmit or distribute power and electricity which directly or indirectly serves the public. A small utility company servicing a small community or limited number of neighborhoods would normally meet the test of providing service to the public. In contrast, if a facility provides direct, dedicated services to a private corporation with no service to the public at large, the line would be considered private. If the line is for the use of a State or local governmental unit, then the line would be viewed as a utility facility.³ Since the Federal definition for “utility” is so broad, FHWA allows the State’s more restrictive definition to determine qualification.

The FHWA-approved State Utility Accommodation Policy (UAP) regulates utility installations on all highways.⁴ If the State definition of a utility includes renewable energy projects, a State can approve installation of these projects in accordance with the process outlined in the UAP without referral to FHWA. The State DOT then enters into written arrangements with a utility (generally in the form of special use permits or joint use agreements). The FHWA Division Office reviews and approves new UAPs and revisions to UAPs for compliance with Federal requirements.

If a project does not qualify as a utility under State law, the project may request to use the ROW through a ROW Use Agreement (previously called Air Space Agreement),⁵ which involves a site-specific Federal approval. Fair market rent is required for land, unless the project is in the public interest based on social, environmental, and economic considerations, in which case an exception must be approved. An application for a ROW Use Agreement approval must include planning and design details about the project, including provisions for maintenance access, terms of use, maps, plans, and sketches.

Due to the programmatic nature of the UAP, it is likely more straightforward for States to pursue renewable energy projects under this approach, rather than through a ROW Use Agreement. If renewable energy is not currently included in a State’s UAP, the State could consider including it during a UAP update.

The FHWA Office of Real Estate Services maintains a map of ROW renewable energy projects, including solar, wind and hydroelectric projects. Peer exchange participants were encouraged to submit projects in their States for inclusion on the map.

Figure 1: Solar panels at the Framingham Service Plaza on Interstate 90 (Source: Volpe Center)

Peer Presentations

The peer exchange involved presentations from State DOT staff who discussed their agencies’ planned and recently implemented highway ROW renewable energy projects. Practitioners from Massachusetts, Vermont, Maryland, Minnesota, Georgia, and Texas discussed their work and experiences.

Massachusetts DOT – Donald Pettey and Lily Oliver.  In 2012, motivated by a State greenhouse gas emissions reductions law (the Massachusetts Global Warming Solutions Act) and State and Federal incentives for solar energy, the Massachusetts DOT (MassDOT) started exploring the idea of ROW solar. To identify appropriate sites for solar panels, MassDOT staff, with support of a consultant, did a desktop review of 600 MassDOT properties and site visits to approximately 60 sites. They then vetted 16 of the most promising sites with the MassDOT real estate office. In July 2013, MassDOT issued a request for response (RFR) for the development of 6 megawatts (MW) of ROW solar projects across multiple sites. In October 2014, MassDOT awarded a contract and worked with the contractor to establish a master license agreement and power purchase agreement. Each project includes a site-specific addendum within the broader master license agreement.

Figure 2: Solar canopy at a MassDOT training and research facility in Hopkinton (Source: Volpe Center)

After MassDOT’s presentation, peer exchange participants visited select MassDOT solar projects along the Massachusetts Turnpike (Interstate 90): a 318kW installation at the Framingham Service Plaza (see Figure 1), and a 490kW solar canopy over a parking lot at the MassDOT Research and Material Lab in Hopkinton off of I-90 (see Figure 2). Moving forward, MassDOT is interested in pursuing other ROW solar projects, including solar noise barriers, solar canopies at park and ride lots, integration with buildings as facilities are upgraded or reconstructed with goals of targeting zero net energy and LEED certifications, and adding a solar/storage component to electric vehicle charging stations.

Vermont Agency of Transportation – Daniel Dutcher

Figure 3: Solar panels at the Fair Haven, Vermont Welcome Center (Source: VTrans)

In 2016, VTrans developed a Solar Plan to explain to the public why VTrans is interested in investing in solar, describe a process for identifying suitable ROW solar sites, and outline information about financial and technological specifications. To better facilitate solar development in the ROW, VTrans amended its UAP by adding a new section on renewable energy generation. VTrans worked with the FHWA Vermont Division on this update, using MassDOT’s UAP as a model.

One challenge to ROW solar development in Vermont is current regulatory uncertainty about net metering. A new net metering rule that was passed in 2017 includes a 500 kW per customer limit. VTrans is considering whether a State agency with multiple locations should be considered a single customer or multiple customers. Additionally, the Vermont Department of Public Service (DPS) may change the net metering rules again in the next legislative session. Moving forward, VTrans plans to track any developments related to the net metering rules and to work with the DPS and the Department of Buildings and General Services to obtain clarity on the net metering program and identify projects that may be feasible without the benefit of net metering.  They will also be organizing inter-agency coordination as part of the State energy planning process.

Maryland DOT – Laura Rogers

The Maryland DOT is pursuing renewable energy opportunities across all of its business units. Several State programs encourage the use of renewable energy, including a renewable energy portfolio standard, a greenhouse gas reduction goal, a community solar pilot program, and a net metering/meter aggregation program. In 2016, the Maryland DOT conducted a preliminary solar evaluation in which it identified 86 sites for potential solar development, representing 60 MW of capacity. In June 2017, Maryland DOT released a Request for Proposals (RFP) through which it will prequalify master contractors to develop solar, geothermal, and microhydro projects on DOT property. The RFP will likely lead to Master Services Agreements with the selected contractor(s), while standard power purchase and lease agreements will be developed for each site. Maryland DOT plans to incur no upfront costs, and the selected contractor(s) will be responsible for operations and maintenance of the systems.

The Maryland DOT faces a challenge of lack of space for renewable energy projects. Due to regulations to protect and restore the Chesapeake Bay, the DOT discourages felling trees and is actively pursuing all available space to plant additional trees. To address these space limitations while expanding ROW renewable energy usage, the DOT is considering innovative solutions such as planting prairie grass mixes under solar panels to mitigate the impact of felling trees,⁶ and developing solar noise barriers.

Minnesota DOT – Ryan Gaulke

A 2007 State greenhouse gas emissions reductions law and a 2013 law requiring State agencies to obtain 1.5 percent of their electricity from solar power motivated the Minnesota DOT (MnDOT) to consider ROW solar. In 2014, MnDOT released a two-stage RFP; the first stage asked developers to identify potential sites for ROW solar, and the second stage involved site-specific proposals. In stage 1, six responders identified 33 sites, which MnDOT narrowed down to 4 responders and 16 sites based on site selection criteria and feedback from district-level staff. In the stage 2 RFP, MnDOT received responses from two developers about seven of the proposed sites. When MnDOT was ready to move forward with specific plans for the sites, it stopped hearing from the developers, who may have been concerned about the long time frame associated with the proposed agreement or the fact that some grants and incentives had expired.

Despite this setback, MnDOT has recently reinvigorated its solar development process with a few changes. A deadline in the State’s solar garden program was approaching in 2016, and several developers approached MnDOT about implementing a project that would qualify for these incentives. One of the proposed projects is a solar canopy on a parking garage in downtown Minneapolis. MnDOT reached an agreement with a developer for the project just before the solar garden program’s deadline. The developer now has two years to design and finance the project, and if the develop is unable to make the project profitable, it is allowed to leave the agreement.

MnDOT has learned several lessons through these experiences, such as the importance of educating staff and getting buy-in at the district level, and the value that a champion at the staff or leadership level can provide. Moving forward, MnDOT is considering putting together a solar energy plan, using a master license agreement, and/or hiring a consultant to help jump-start a larger ROW solar program.

Georgia DOT and The Ray – John Hibbard and Allie Kelly

Figure 4: The Wattway drivable solar road surface at the I-85 Visitor Information Center along The Ray (Source: The Ray)

Several of these innovations relate to ROW renewable energy. At the I-85 Visitor Information Center, The Ray has piloted a solar electric vehicle charging station and a drivable solar road surface called the Wattway that is the first deployment of the technology outside of France (see Figure 4). The Ray has also planned a 1 MW solar ROW project that is expected to come online in 2018. Georgia Power plans to finance and build the project, which will supply electricity to the grid. The Ray is working with partners to design the project as a pollinator-friendly pilot, which will involve planting seed mixes that attract pollinators around the panels, rather than planting the typical turfgrass or covering the area with gravel. The project is currently proceeding despite a lack of State incentives and a highly regulated utility market that presents challenges to implementing ROW solar in Georgia.

The GDOT has worked closely with The Ray on these projects, and in many cases The Ray has been able to encourage GDOT to test strategies that it may not otherwise have had the funding or capacity to try. GDOT has also permitted these projects; for example, it allowed the Wattway through an encroachment permit. In the future, The Ray, in partnership with GDOT, is considering several additional innovations, including integrated solar noise barriers, ROW wind generation, and ROW farming.

Texas DOT – Beverly West

Texas has abundant solar resources and volatile natural gas prices, which has motivated the Texas DOT (TxDOT) to explore renewable energy project possibilities. Since 2006, State agencies utilize a State procurement contract to purchase electricity in the deregulated market from retail electric providers, which typically use contract terms of up to four years. In 2015, TxDOT partnered with other state agencies to request a new state contract or changes to the current contract to allow expanded purchasing opportunities. In the meantime, TxDOT negotiated a new contract at a historic low rate ($0.03/kWh for electricity, not including transmission charges) for 100 percent renewable sourced energy with the renewable energy credits to be placed in Texas. This led to TxDOT savings of $5 million over the previous year. In 2017, a new statewide contract was implemented, which includes opportunities for power purchase agreements for wholesale renewable energy, coordinating on-site solar with energy contracts, and financial incentives for conserving energy during times of peak demand.

With this new electricity procurement contract in place, TxDOT can now more easily pursue ROW renewable energy opportunities. Accordingly, TxDOT is currently planning a ROW solar project in partnership with the Central Texas Regional Mobility Authority adjacent to Austin Bergstrom International Airport at the intersection of two State highways. The project will be the first highway ROW solar project in the State.

Key Takeaways

Several key themes emerged during the peer exchange. Participants discussed the importance of obtaining buy-in across the agency for ROW renewable energy projects, from the leadership level to the field staff levels where personnel are familiar with the ROW sites where renewable projects could be implemented. Interagency coordination can also help agencies to implement ROW renewable energy projects; the DOT typically plays a leadership role since it owns the ROW, but agencies such as a department of energy, public utilities commission, or the department responsible for managing State buildings may have experience with developing renewable energy projects and be able to provide valuable advice and technical assistance.

Most of the ROW solar projects discussed by peer exchange participants are public private partnerships, where the developer finances the project up front and manages its operations and maintenance. States benefit from these arrangements by having a dedicated source of renewable energy to purchase at a guaranteed rate, and in some cases by taking advantage of State net metering incentives. These projects are profitable for developers because they get to take advantage of State and Federal incentives for renewable energy, and have a guaranteed source to sell the electricity to under a long-term contract. In several cases, States have signed master license agreements with contractors to develop multiple solar ROW projects, to which site-specific stipulations are added.

States have pursued different strategies to identify potential sites for ROW solar. In most cases, a State has done an evaluation of all (or a large number of) DOT sites using specific criteria, such as setback from the ROW, access for maintenance, and cardinal orientation and angle of inclination. In one State, the DOT let developers propose sites for ROW solar development. However, the State encountered challenges with this approach since the district offices did not have buy-in for the site selection. Some States with space constraints are considering alternate ways to implement ROW solar, such as solar panels on DOT buildings or solar noise barriers.

State incentives play an important role in determining whether a ROW solar project will be profitable. State net metering programs, where renewable energy can be sold back to the utility at the retail rate, have helped States make ROW projects pencil out. As solar power becomes more widespread and costs come down, many States are considering eliminating or changing their net metering policies.

At the conclusion of the peer exchange, participants were asked what resources from FHWA would help them implement ROW renewable energy projects. Participants suggested that technical assistance for FHWA Division Office staff would be helpful, so that when State DOTs have questions or need approvals the Division Offices would know the requirements and that FHWA headquarters is supportive. FHWA is considering publishing a Frequently Asked Questions document to clarify the requirements associated with ROW renewable energy.

More Regulatory Details

Federal Regulations

Prior to 1988, FHWA prohibited the installation of utilities within interstate ROW, and many states adopted the same policy for state highways. In 1988, that policy changed to allow each
state to decide whether to permit utilities within interstate ROW and to specify the conditions for approval, or continue to adhere to the stricter AASHTO policies. The 1988 FHWA policy also stated that public utilities (i.e., utility service available for public use) that were “in the public interest” could be allowed in interstate ROW under the DOT’s approved Utility Accommodation Policy (UAP) Manual or Plan as long as they are accommodated in ways that are safe for the traveling public and do not interfere with the operation of the facility. The emergence of opportunities for locating renewable energy technologies and alternative fuel facilities within highway ROW has caused FHWA and the states to reexamine the existing definition for “utility.”

At present, a number of Federal statutes and regulations govern the use and management of the highway ROW. The Federal statutes and regulations most applicable to accommodating
renewable energy generating technologies and alternative fuel infrastructure in the ROW are:

• 49 Code of Federal Regulations (CFR) 18.31(b) (Real Property)
• 23 United States Code (USC) 111 (Use and Access to ROW)
• 23 CFR 645 Subpart B (Accommodation of Utilities)
• 23 CFR 710 (ROW and Real Estate)
• 23 CFR 752.5 (Safety Rest Areas)

Some current Federal restrictions on highway real property use and commercialization may limit state DOTs’ abilities to construct renewable energy technologies or alternative fuel facilities
along the highway ROW. The use of highway real property is limited by 49 CFR 18.31(b), which states that except as otherwise provided by Federal statutes, real property will be used for
the originally authorized purposes as long as the property is needed for those purposes.  Commercialization along the interstate highway system is also restricted. Specifically, 23 USC 111 requires states, as a condition of receiving Interstate funding, to prohibit automotive service stations or other commercial establishments for serving motor vehicle users to be constructed or located on the ROW of the Interstate System. Federal regulations further prohibit states from charging the public for goods and services at safety rest areas except for telephone and vending machines (23 CFR 752.5).

A provision of SAFETEA-LU amended 23 USC 111 by adding subsection (d), permitting idling reduction facilities to be installed at safety rest areas on the Interstate for commercial vehicle use; subsection (d) permitted the charging of a fee for the use of those facilities. (These would be plugs and ability to charge/run appliances and air conditioning in trucks) However, three years later, this provision was repealed. The Administrator can still approve under 23 CFR 1.23 any noncommercial uses on the ROW if they are in the public interest and will not interfere with the free and safe flow of traffic.

Additional regulations govern the use of the Interstate ROW for utilities (23 USC 109(l) and 23 CFR 645). A utility is determined to be “public” by how a state defines the term under its own laws and regulations as well as whether it meets the Federal definition.8 As defined in Federal regulation, a utility is a “privately, publically, or cooperatively owned line, facility or system for producing, transmitting, or distributing communications, cable television, power, electricity, light, heat, gas, oil, crude products, water, steam, waste, storm water not connected with highway draining, or any other similar commodity, including any fire or police signal system or street lightening system, which directly or indirectly serves the public” (23 CFR 645.207). DOTs can accommodate public and private utility facilities within the ROW when such facilities serve the public interest under their approved Utility Accommodation Policy (UAP) Manual or Plan (per 23 CFR 645 Subpart B). The UAP describes practices and procedures for regulating and accommodating utility facilities along, across, or on highway ROW and other transportation facilities under their respective jurisdictions. AASHTO’s “Guide for Accommodating Utilities within the Right-of-Way”9 establishes guidelines for states’ UAPs, which FHWA ultimately reviews and approves.10

The use of highway ROW to accommodate facilities that will serve private or proprietary interests may also be accommodated; however, it is necessary for them to be approved under the
airspace leasing requirements of 23 CFR 710 Subpart D. The right to use the ROW for interim non-highway use may be granted in airspace leases as long as such uses will not interfere with the construction, operation or maintenance of the facility; anticipated future transportation needs; or the safety and security of the facility for both highway and non-highway users.11 The DOT shall charge current fair market value or rent for the use of the land; the income received from airspace leases shall be used for transportation purposes (as specified is 23 CFR 710.403(e)).

Federal regulations do provide an exception to charging fair market rent if the DOT shows and the FHWA approves, that such an exception is in the overall public interest for social, environmental, or economic purposes. This exception may be appropriate for activities that address climate change mitigation and adaptation or contribute to improvements in air quality.

The FHWA has final approval on leases of airspace on Interstate systems. On March 27, 2009, FHWA’s Office of Real Estate Services and Office of Program Administration jointly issued guidance on the longitudinal accommodation of utilities in the Interstate System ROW. (FHWA’s HEPR and Office of Program Administration March 27, 2009. Information: Guidance on Utilization
of Highway Right‐of‐Way. Longitudinal Accommodation of Utilities in the Interstate System Right‐of‐Way. www.fhwa.dot.gov/realestate/guidutil.htm_

The guidance provides an expanded discussion on how 23 CFR Part 645 and 23 CFR Part 710 apply to utility accommodation proposals based on the classification of the facility’s intended use.
Whether accommodated under a DOT’s approved UAP or through an airspace lease, use of the highway ROW requires some form of written agreement. The terms of the agreement define the
responsibilities and authorities of the parties involved, typically the DOT and the utility company. Additionally, the agreement should include provisions governing lease revocation; removal of improvements; adequate liability insurance to hold the DOT and the FHWA harmless; requirements of the utility; and access by the transportation agency for inspection, maintenance, and reconstruction of the transportation facility. The DOT should also have the capacity, policies, and procedures in place to verify the desired operation is progressing as planned and not adversely affecting highway safety and traffic flow.

Finally, each action in the highway ROW that is classified as a major Federal action must comply with the National Environmental Policy Act (NEPA) and other relevant environmental regulations. Federal actions are projects that use Federal funding, require a Federal permit, or require a Federal agency’s approval.13 The appropriate NEPA class of action is determined by the significance of the environmental impact of the project under study. Actions in the highway ROW that do not individually or cumulatively have a significant effect on the environment, for example, may be covered under a Categorical Exclusion level document.

29 states allow for the use of highway ROW to accommodate public utility facilities as noted in FHWA’s Guidance on Utilization of Highway ROW. Five other states allow for utilities in highway ROW when certain exceptions are made, such as allowing for telecommunications utilities only (Colorado), utilities on highways but not the Interstate (Nebraska), or the longitudinal placement of high-voltage transmission lines–potentially for compensation–when there is no other practical alternative (Florida).

However, most states (29) also indicated that their UAPs do not characterize renewable energy facilities as utilities in regard to accommodating them in highway ROW. In one state, the definition of the term “utility” refers to the lines used to distribute power, not the means to generate it. In other states, the UAPs do not make distinctions between renewable and nonrenewable energy facilities. Some states noted that while renewable energy facilities are not specifically distinguished as utilities in their UAPs, the permissibility of those facilities would likely be open to legal interpretation. (In Ohio, the DOT does differentiate between renewable energy facilities and other utilities in describing the former as “alternative energy utilities.” Ohio DOT anticipates that the 2011 update to its Utilities Manual will directly address the topic of accommodating renewable energy facilities in the state’s highway ROW.)

Nevertheless, fundamentally most states (36) do not have any laws or other requirements that either allow or prohibit the generation of renewable energy within highway ROW. No specific
legal authorizations or proscriptions have been given in these states. Of the remaining three states for which responses were received, two have laws allowing for the accommodation of renewable energy facilities in highway ROW while the third has an encroachment policy that may discourage some types of renewable energy technologies, such as wind turbines, within the ROW.

…generating renewable energy within highway ROW is an emerging concept in the United States.

Several state DOTs, including Colorado, Massachusetts, Texas, Ohio and California are
conducting comprehensive statewide renewable energy feasibility studies to identify promising renewable energy technologies and locations to implement them.

(pp. 15-16) In 2010, the Colorado DOT (CDOT) evaluated the alternative energy source potential, including wind, solar, biocrop, geothermal, and hydropower, of its ROW, facility grounds, building rooftops, and other built features.20 A previous study conducted by the Colorado Governor’s Task Force on Renewable Energy Generation had identified areas of the state with strong renewable resource potential.21  CDOT ROW maps were superimposed with geographic information system (GIS) data layers of each alternative energy type to calculate the total energy potential within usable CDOT ROW. CDOT classified “usable ROW” based on resource-specific criteria, including slope, ROW width and accessibility, proximity to existing electrical transmission, and potential for CDOT usage (see Figure 1).

20 Colorado State University–Pueblo. March 2011. Assessment of Colorado Department of Transportation Rest Areas for Sustainability Improvements and Highway Corridors and Facilities for Alternative Energy. Source Use. Prepared for Colorado DOT. www.coloradodot.info/programs/research/pdfs/2011/restareas/at_download/file
21 The Colorado Governor’s Task Force on Renewable Resource Generation “Connecting Colorado’s Renewable Resources to the Markets” mapped and evaluated Colorado’s solar, wind, and hydroelectric power, as well as geothermal and biomass resources. The report is available at
http://rechargecolorado.com/images/uploads/pdfs/redi_full%5B1%5D.pdf.

MassDOT is currently conducting a similar statewide assessment of the Highway Division’s real estate holdings, including buildings, structures, and ROW, to identify potential sites suitable for large- and small-scale wind and solar installations. To identify potential sites, GIS data on MassDOT facilities and other land holdings will be overlaid on solar and wind resource data, such as the National Renewable Energy Laboratory’s (NREL’s) 50-meter wind power data for Massachusetts. MassDOT holdings that are located in areas with quality wind and solar resources will be further assessed against a set of resource-specific suitability criteria, such as acreage, existence of environmental constraints, proximity to existing electrical transmission, and feasible construction access. Study results were expected in mid to late 2011.

The Oregon Department of Transportation (ODOT) has also conducted a statewide GIS analysis of its operating and non-operating ROW for potential additional solar highway project
sites. ODOT has identified over 600 additional sites and is in the process of applying additional criteria to narrow down an inventory of truly feasible sites. ODOT may further utilize this data
and perform additional analysis in a future phase to search for sites for other types of renewable energy projects such as wind, biocrop, or public electric vehicle (EV) charging infrastructure.
Similarly, the Ohio DOT is partnering with the Ohio State University to utilize GIS to identify opportunity zones for renewable energy and other revenue generating projects in the highway
ROW. The research effort will utilize numerous GIS layers, including DOT assets and wind and solar resource maps, coupled with an economic analysis to identify priority locations, or
“opportunity zones,” for potentially implementing future renewable energy and alternative fuel projects.

The Texas Department of Transportation (TxDOT) is working with the University of Texas at Austin’s Center for Transportation Research (CTR) to investigate opportunities to extract additional value for highway ROW and other DOT land holdings through various applications, including air right agreements, joint development initiatives, and implementing renewable energy technologies in the ROW. The CTR study will assess when, where, and under what circumstances to pursue specific applications. At the end of the assessment, which is scheduled for early 2012, CTR will develop guidance on when to pursue implementation of a value extraction application, including how to identify and involve key stakeholders.

At the national level, the National Cooperative Highway Research Program (NCHRP) 25/25 Task 64: Feasibility Study of Using Solar or Wind Power for Transportation Infrastructure,22
completed March 2011, provides an overview of current and emerging technologies used in wind and solar applications. The report presents a general design approach for installations located
near the roadway ROW and includes a tool for performing life-cycle cost analysis to determine the feasibility of potential transportation-related renewable energy installation projects.
Similarly, NCHRP 20-85: Renewable Energy Guide for Highway Maintenance Facilities, completed in July 2012, developrf best practices for the planning, design, and operation of
new and retrofitted highway maintenance facilities that are sustainable and energy efficient over their service lives through the effective use of energy capture technologies, including active,
renewable energy sources and passive building and site modifications.

In the eastern U.S., Ohio DOT has partnered with the University of Toledo to deploy a solar array within the highway ROW to offset the electricity demand and operating costs associated
with a 196-foot light-emitting diode (LED) lighted structure on the Veteran’s Glass City Skyway bridge near Toledo, Ohio. The 100kW test array, which consists of both rigid and flexible solar
panels (see Figure 7) made in Ohio, will be used to help Ohio DOT evaluate, select, and procure equipment for future permanent solar installations within the highway ROW, as well as to
identify problems that are unique to alternative energy projects implemented in such a manner.

Several other states have solar energy projects underway. MassDOT is coordinating with the Town of Carver, Massachusetts, to permit the installation of a solar array along Route 44, an
east-west state highway in a southeastern part of the state. The Town of Carver, which has recently constructed a new water treatment facility in the North Carver Water District, is interested in installing a 112 kilowatt (kW) PV system to support the water system’s energy needs. In November 2010, the town selected a preferred vendor, who will install, own, and operate the solar panels. The Town will purchase the renewable electricity from the vendor. Construction of the solar facility was completed in 2012.

Beginning in 2008, the California Department of Transportation (Caltrans) and the Sacramento Municipal Utility District (SMUD) worked together in an effort to develop solar energy projects
at two potential sites along Highway 50 in Sacramento County. The projects were expected to have a planned capacity of 1.4MW and utilize both traditional PV and CPV technologies. SMUD
completed the environmental review26 for the project in July 2011 and a conceptual draft airspace lease agreement that would have governed SMUD’s use of the Caltrans ROW was
approved in August 2011. SMUD then issued a Request for Offers to identify a partner to design, construct, and operate the solar systems. SMUD only received one bid for construction, which
was priced higher than anticipated. As a result, SMUD determined that the solar highway project was not economically feasible at this time.

Caltrans also has also proposed to enter into a partnership agreement (airspace developmental lease and revenue share operations agreement) that would permit Republic Cloverleaf Solar,
LLC (Republic) to install and maintain flat-plate solar panels within operating ROW at up to seven interchange locations throughout Santa Clara County. Republic would develop, finance,
construct, own, operate, and maintain the PV systems, which combined would generate up to 15 MW of power to be sold directly to an investor or municipally owned utility. The airspace lease
agreement would allow for the production of renewable power facilities on otherwise unleasable ROW, while establishing a new revenue source for the State. The draft environmental document
for the project has been completed.27

26 SMUD released the Revised Final Sacramento Solar Highway Initial Study and Mitigated Negative Declaration in July 2011. The document is available at www.smud.org/en/about/Documents/ceqapdfs/solar‐highways‐final‐july11.pdf.

Nationally, the “Adopt-A-Watt™ Program,” which is based on the Adopt-A-Highway program, is seeking to promote energy conservation by giving sponsors community recognition for
funding of clean energy, alternative fuel, and energy-efficiency projects. New Jersey DOT (NJDOT) is currently assessing the possibilities for constructing solar light poles and PV arrays
at its rest areas as a part of the Adopt-A-Watt program. NJDOT’s proposal has other precedents; all of the 19 rest areas that Wyoming DOT opened since 1980 use solar power to provide an
estimated half of the rest areas’ energy needs, a trend that is expected to continue. Additionally, in August 2010, solar “flowers,” or solar panels in the shape of flowers, began producing
electricity at a rest area on Interstate 70 near Parachute, Colorado (see Figure 8 I‐70 rest area solar flowers in Parachute, CO Photo credit: www.garfieldcleanenergy.org).

Additionally, in April 2010, the FHWA entered into a cooperative agreement with the University of Nebraska-Lincoln to explore developing a Roadway Wind/Solar Hybrid Power Generation and
Distribution System. The system would incorporate wind and solar hybrid energy harvesting systems with a “microgrid” that manages the energy produced with demand from surrounding infrastructure but that could interact with the overall power grid in the case that the microgrid needed additional energy, had excess energy to provide, or needed to isolate itself from disruptions in the larger power grid. The research effort will involve laboratory-scale testing and modeling of appropriate systems, followed by a fullscale installation and testing program.

Solar Power Applications in the Roadway

Transportation engineers have also sought ways to generate and/or use solar power directly from or in the roadway. A British company, for example, has developed a road stud that contains small solar panels and automatically emits LED light to illuminate roadways when it becomes dark outside. The solar panel road studs have been installed in over 120 roads in the UK and in locations in the Noord-Holland Province of The Netherlands.28 Domestically, as of August 2010, the Washington State DOT (WSDOT) began a 5 year test of the same technology along a 2 mile section of State Route 530 that has a history of run-off-the-road collisions.29 The solar-powered road reflectors (see Figure 9) that WSDOT has installed contain an LED that automatically light up under dark conditions to provide an estimated 10 times greater visibility for drivers than the traditional retro-reflective markers. Depending on the results of the tests and available funding, WSDOT will consider investing in additional test areas on other roadway surfaces or situations. (See WSDOT solar reflector Photo credit: WSDOT, www.flickr.com/photos/wsdot/)

The UK has also conducted successful trials of using inter-seasonal heat transfer systems that incorporate solar energy collectors in the road and shallow insulated heat stores in the ground.30 Likewise, Worcester Polytechnic Institute researchers have found evidence suggesting that asphalt pavement solar collectors hold promise for energy recovery.31 In more exploratory research, the Idaho-based company “Solar Roadways” has been awarded Small Business Innovation Research grants to develop 12-by-12-foot solar panels that could be embedded into roads to provide power into the electrical grid. It is estimated that each solar road panel, which would cost approximately $7,000 each, could generate roughly 7.6 kWh of power per day. Researchers are investigating whether the panels could feature LED road warnings and built-in heating elements that could prevent roads from freezing.

Washington State DOT August 17, 2010 Press Release. www.rtands.com/newsflash/carmanah‐trojanbattery‐ enter‐into‐strategic‐partnership.html Last accessed February 14, 2011.

Wind

To date, only a few state DOTs have examined the feasibility of installing wind turbines in highway ROW with most potential applications being at highway rest areas or on facilities. The
Ohio DOT, for example, is installing a small 32 kW wind turbine at a maintenance facility in Northwood, Ohio. The maintenance facility is located adjacent to the highway ROW along I-68.
The electricity produced by the turbine will be used on site, and Ohio DOT anticipates that it will help meet up to 65 percent of the electricity needs of the maintenance facility.

The former Massachusetts Turnpike Authority, now part of MassDOT, analyzed potential wind turbine sites along the Massachusetts Turnpike, a 138-mile highway extending across the state from east to west, in support of the state’s Leading by Example Program that established GHG emissions reduction and renewable energy targets for all of the state’s agencies. One of the sites
the Turnpike Authority examined was a 68-acre property it owned in the western part of the state. The land holding is adjacent to the Blandford service area (see Figure 12). Over 13 months,
the Turnpike Authority conducted a feasibility study, collecting wind speed and other site condition information.35 It was ultimately determined that the site was suitable for wind power
development, and in April 2009, the former Turnpike Authority issued a Request for Proposal (RFP) for a long-term lease for wind turbine development at the service area. Solaya Energy,
LLC was selected to develop what was planned to be a nearly 400-foot tall, 1.5 MW wind turbine. However, in May 2011 registered voters at a Town of Blandford open town meeting defeated a wind power zoning bylaw that would have allowed the development of the proposed turbine, putting the future of this project in question.

In 2009, the University of Illinois at Urbana Champaign investigated use of wind for providing electrical power at Illinois DOT highway rest areas and weigh stations to determine the extent to
which wind power could offset electricity costs and energy use and provide a reasonable return on investment.36 The study, which identified several favorable sites where installing small wind
turbines could be economically feasible, found that one of the most important determinants of return on investment and viability was the cost of the wind turbines—a variable consideration
that depends on many factors. The team developed a spreadsheet that enables procurement agents to rigorously compare the prices and returns for given locations and turbine manufacturers. See Table 2 for example wind energy activities along highways globally.

Prok, Joshua. Spring 2008. Interstate Wind: Using New Technology to Enhance Transportation Fuel Investments. Transportation Law Journal. 35(67).

Chapman and Wiczkowski 2009. Wind‐Powered Electrical Systems – Highway Rest Areas, Weigh Stations, and Team Section Buildings. Illinois Center for Transportation.  http://ict.illinois.edu/publications/report%20files/FHWA‐ICT‐09‐034.pdf

Biofuels

Several agencies are beginning to explore the potential for bioenergy generation in highway ROW through the Freeways to Fuel (F2F) National Alliance. The F2F program investigates the
use of non-traditional agronomic lands such as roadside ROW, military bases, and airports for the growth of biofuel feedstock crops across the country. Freeways to Fuel seeks to increase the
production of biofuel without effecting food, fiber, feed, or flower production by targeting lands that are not currently in production It began in 2006 as a cooperative program between the Utah
DOT (UDOT) and Utah State University (USU). UDOT was interested in learning whether it could use its ROW to produce alternative fuel feedstock and reduce maintenance costs. The two
organizations decided to pilot test the planting and cultivation of safflower and canola in eight 20-foot by 8-foot plots in four different locations along the I-15 corridor. Ultimately, arid conditions and heavily compacted soil led the team to conclude that growing biocrops in Utah faces significant challenges that might not be manifested in other states. To address this issue, USU developed an aerator tool that could be attached to state DOTs’ planting equipment. Based on lessons learned from the Utah pilot, USU developed a set of criteria by which the feasibility of a potential ROW biocrop program could be evaluated. The criteria included crop type, erosion, structural integrity of the road and ROW, habitat issues, line of sight issues, risk management issues, ecological impacts, and water quality issues.

Since that time, the alliance has grown to include other State DOTs and land grant universities.38 The North Carolina F2F project started in 2009 and is now largely regarded as one of the most
promising programs in the Alliance. Its moist climate, fertile soils, and support from the State legislature have made North Carolina DOT’s (NCDOT) biocrop growing efforts a national
model. The North Carolina project began with four 1-acre plots of canola or sunflower crops (see Figure 13). The NCDOT, in coordination with North Carolina State University, selected crops
that it believed would provide the greatest yield in the ROW. By working with seasonally rotated crops on the same plot, NCDOT has been able to meet or exceed national standards for crop
production. In 2010, NCDOT extracted 3,000 lb of canola seed, which produced 100 gallons of virgin oil. This in turn created 150 gallons of B100, which was cut with conventional diesel to produce approximately 600 gallons of B20 product that NCDOT used to power its dump trucks, tractors, and other equipment. Media coverage and public feedback for the effort have been overwhelmingly positive. As of August 2011, NCDOT has its fourth crop planted.

In Tennessee, its DOT and Genera Energy LLC recently planted several plots of switchgrass along Interstate corridors in the state (see Figure 14). The test plots are designed to demonstrate if switchgrass can help reduce maintenance costs by reducing the need for mowing, while having the added benefits of producing biocrops for cellulosic ethanol production and reducing erosion at highway interchanges. Likewise, there are other state DOTs, such as those in Oregon, Texas, and Washington (among others), that are working to identify potential ROW locations for biocrop plots. Similarly, Michigan DOT has identified 10,000 ROW acres for planting, which it plans to offer to bid in the near future. See Table 2 for example bioenergy activities on highway ROW.

Energy Harvesting and Highway ROW

Energy harvesting technologies could convert ambient energy of various forms (e.g., stress and strain, mechanical, vibrations and noise) into electrical energy. Some systems, such as wave or tidal power technologies, directly convert kinetic energy into electricity. Other technologies, such as piezoelectric materials, “scavenge” energy from ambient vibrations.

In the case of wave and tidal power, energy from the ocean can be converted into electricity or other useful forms of power with turbines placed underwater. Given that 78 percent of United
States’ electricity consumption occurs in a state bordering an ocean or a Great Lake,39 wave and water currents could be significant and virtually untapped renewable energy resources near or
within highway ROW. This concept has been effectively demonstrated in Sweden, Scotland, and other European countries, such as France, where plans have been made to install eight turbines
underneath bridges crossing the River Seine in Paris, France.40 Wave energy applications in roadway settings are only beginning to emerge in the U.S. as compared to other renewable
energy technologies. For example, in 2006, newspapers reported that city officials were considering submerging wave turbines at the Golden Gate Bridge to capitalize on the strong
currents often measured there.41 After several years of debate, the project was ultimately deemed too expensive to pursue.  As reported in June 2010, Hawaii DOT is participating in
early discussions for the accommodation of power lines in the ROW for wave energy transmission.

40 Wilssher, Kim. June 28, 2010. Paris looks for power from turbines beneath the Seine. The Guardian. www.guardian.co.uk/world/2010/jun/28/paris‐power‐turbines‐seine
41 Vega, Cecilia. September 19, 2006. Tides around Golden Gate are potential energy source. The San Francisco Chronicle. www.sfgate.com/cgi‐bin/article.cgi?=/c/a/2006/09/19/BAGKJL872O1.DTL

Using technologies that capture energy from roadway vibrations (see Figure 15) currently appears to be a more practical prospect for highway ROW renewable energy generation, though
they are still comparatively unproven technologies when balanced against solar power, wind power, and bioenergy applications. For example, the Israeli company Innowattech is working
with an Italian infrastructure and civil engineering contractor to use generators placed beneath the upper layer of asphalt on a highway to light road signs between Venice and Trieste, Italy.
The generators will harvest the electrical charge that the vibrations of the moving vehicles create.42 Other companies are exploring opportunities to capture the energy lost in the process of
a vehicle braking to generate electricity. The lost energy is captured via specially designed mats, which are installed on the road in places where vehicles slow down.43

Recently, FHWA has contracted with Virginia Tech University to investigate “energy independent” monitoring systems for bridges. The proposed systems would use piezoelectric
materials to harvest electricity from the vibrations in the bridge that the vehicles crossing over it create.44 Likewise, researchers at the University of Minnesota Duluth are developing a
piezoresistive mixture of concrete with embedded electrodes in an effort to measure the change in electrical resistance that the stress of passing vehicles generates.45,46

42 For more information, see www.greenprophet.com/2010/05/israel%E2%80%99s‐innowattech‐toprovide‐renewable‐energy‐for‐highway‐signs‐in‐italy/ and http://spectrum.ieee.org/green‐tech/masstransit/startups‐try‐to‐capture‐road‐traffics‐excessenergy/?utm_source=techalert&utm_medium=email&utm_campaign=101410
43 For example, the American company New Energy Technologies Inc. and the UK’s Highway Energy Systems Ltd.
44 Virginia Tech University. www.vtnews.vt.edu/articles/2009/02/2009‐77.html
45 ITS Institute. “Beyond the loop: Researchers develop the next generation of vehicle detectors.” The Sensor Newsletter. Spring 2009.  www.its.umn.edu/Publications/Sensor/2009/01/BeyondtheLoop.html
46 As a part of its Technology Innovation Program, the National Institute of Standards and Technology sponsors research into new technologies that will enable an easily deployed, self‐powered network of wireless sensors, together with analysis tools, to provide continuous monitoring of the structural integrity of bridges. For more information, see http://tipex.nist.gov/tippb/prjbriefs/prjbrief.cfm?ProjectNumber=080011

Alternative Fuel Facilities in the ROW

Recent Federal energy polices have emphasized Federal agency adoption of strategies to reduce GHG emissions. In conjunction, compliance with Executive Order 13514 has prompted state DOTs to adopt various sustainability measures. In addition to using highway ROW for renewable energy generation, there is an opportunity for transportation agencies to distribute cleaner-burning, alternative fuels along roadways. Doing so could help accelerate the creation of a clean energy economy, promote energy security and offer state DOTs a new source of revenue generation, especially if petroleum prices continue to rise as expected. Finland has been at the forefront of fully exploring these opportunities.

Proponents in the country are proposing to build a $1 billion carbon-neutral highway, the first of its kind in the world, from Helsinki to a city near the Russian border. The system would provide a mix of biofuels, EV charging infrastructure that obtains energy from solar and wind power technologies, and renewable energy generation technologies along the highway. The towns along the highway would be involved in the effort by growing biocrops for biofuel creation. The project is under the feasibility analysis stage and is projected to be completed by 2016 if approved.

The U.S. has established goals for alternative fuels and alternatively-fueled vehicles at both the national and state level. President Obama’s Administration established targets to have one
million plug-in hybrid electric vehicles (PHEV) on the highway by 2015 and to reduce oil use by approximately 3.5 million barrels per day in 10 years.47,48 Accordingly, unprecedented amounts of funding under the US Energy Independence and Security Act of 2007 and the American Recovery and Reinvestment Act of 2009 (ARRA) are being put toward alternative fuels research
and development.

The opportunities for accommodating EV and PHEV charging facilities within highway ROW are likely greater than for the other alternative fuels listed, especially when the electricity is generated on-site by renewable (e.g., solar and wind) sources. This is likely the case due to the fact that EV and PHEV technologies would require new supporting infrastructure, unlike biofuel distribution facilities that could use existing or modified pump and tank storage infrastructure already available at commercial service stations.50 Thus, facilities within highway ROW, such as visitor centers, recreational/natural resource rest areas, truck rest havens, and perhaps some scenic overlooks, may offer convenient locations for new EV and PHEV charging technology.

DOTs could facilitate the development of a charging infrastructure network that supports interstate and regional travel, since routine charging will likely be provided by home- or work-based charging stations or other publicly accessible locations.  The Florida Turnpike Enterprise (FTE), a separate business unit of the Florida DOT, for
example, is currently trying to pilot test this concept as regulatory restrictions on commercial establishments along the transportation system do not apply to turnpike authorities. FTE was
recently approved for six, 500-volt, high-current rapid charging stations that it plans on strategically placing along the Florida Turnpike in south Florida. These stations are in addition to 40 truck electrification stations installed on the turnpike that allow tractor trailer trucks to get heat, air, and electricity without having to idle. Similarly, MassDOT and the Massachusetts Executive Office of Environmental Affairs is working to identify prime locations for public charging infrastructure, particularly at public parking areas and in public-private partnership applications.

The Ohio DOT recently proposed a research project to evaluate the installation of a wind and solar-powered rest stop electrification system at two rest area facilities (see Figure 17). The
project, which was ultimately cancelled due to changing priorities, would have involved installing 12 truck electrification stations (six at each rest area) that allow truck drivers to plug-in
their vehicles and operate onboard devices such as heating, ventilation, and air conditioning (HVAC); computers; and appliances through a window unit or off-board 120-volt power
pedestal. Commercial truck drivers would have used the system free of charge. A wind turbine and a ground mounted solar array system located at the rest area were proposed to power the
electrification systems. FHWA granted conceptual approval of the research proposal, noting that as long as the Ohio DOT did not charge a fee for the use of the truck electrification systems, the activity would have been considered noncommercial, and since the use of the system would reduce fuel consumption and air pollution, the project would have been considered to be in the public interest. 

In 2009 and 2010, the U.S. Department of Energy (DOE) awarded the company ECOtality a grant totaling $155 million to support the “EV Project,” a pilot project to collect and analyze data
to characterize vehicle use in diverse topographic and climatic conditions, evaluate the effectiveness of charging infrastructure, and conduct trials of various revenue systems for commercial and public charging infrastructures. The ultimate goal of the EV Project is to take the lessons learned from the deployment of the first 8,300 EVs, and the charging infrastructure supporting them, to enable the streamlined deployment of the next 5,000,000 EVs. The EV Project selected seven test markets to deploy EV vehicles and charging stations: California, Oregon, Washington, Arizona, Texas, Tennessee, and Washington, D.C. The DOE is also forming a partnership with Google Inc. and more than 80 EV stakeholders to help consumers find charging stations nationwide.

Three of the states participating in the EV project—Oregon, Washington, and California—have also partnered to form the West Coast Green Highway,51 an initiative aimed at advancing the
adoption and use of electric and alternative-fuel vehicles along the I-5 corridor. In October 2008, the three states jointly submitted a New Special Experimental Project (SEP-15) application for
the I-5 Alternative Fuels Corridor Project. The project would allow limited commercialization of state-owned ROW or highway rest areas to promote the use of alternative fuels. USDOT determined that it would be better implemented through modification to the Interstate Oasis Program guidance.52 The necessary change has not been initiated to date. In June 2010, the Governor of Washington announced that WSDOT and the state’s commerce 51 West Coast Green Highway. Available at www.westcoastgreenhighway.com

47 January 2011 State of the Union Address
48 In June 2011, a public comment seeking comments on whether FHWA should grant a waiver of the Buy America requirements of 23 CFR 635.410 to permit the use of non‐domestic 12 all‐battery electric vehicles, 12 plug‐in hybrid vehicles, and 5 neighborhood electric vehicles in the state of California ended. FHWA will publish a notice of finding after considering all comments received.
49 According to the U.S. Census Bureau’s 2007 Economic Census, there are nearly 119,000 gasoline stations in the United States.
50 It should be noted that in California, planning to develop a California Hydrogen Highway Network is
currently underway, and there has been some interest among private developers to support the
establishment of hydrogen refueling stations on the East Coast as well. See  www.hydrogenhighway.ca.gov/
and http://wheels.blogs.nytimes.com/2010/04/16/a‐private‐plan‐for‐a‐hydrogen‐highway/

52 FHWA’s Interstate Oasis Program: www.fhwa.dot.gov/safetealu/factsheets/iop.htm

53 Oregon DOT. Electric Vehicle Charging Network. Available at www.oregon.gov/ODOT/HWY/OIPP/inn_evcharging.
shtml

International and Domestic Examples of Renewable Energy and Alternative Fuel Facilities in Highway ROW

SOLAR ENERGY – DOMESTIC

California: Solar panels are being installed at carports across the state. Caltrans has also been installing solar power generating facilities on state-owned buildings (maintenance stations) and in safety roadside rest areas to offset the cost of the energy Caltrans uses. The facilities are sized so that the DOT does not generate more energy than it uses, thus avoiding being characterized as a utility. Additionally, a Swedish architect’s “solar serpent highway” idea for Santa Monica, CA is in a conceptual phase.

District of Columbia: DDOT has installed solar powered parking meters. Solar lights are in use along the Metropolitan Branch Trail.

Florida: The Florida Turnpike Enterprise has plans to install a solar park at the Turkey Lake Service Plaza.

Hawaii: Hawaii DOT has installed PV power systems at seven DOT facilities, including five airport facilities, a DOT Highways Division baseyard, and a DOT administration building.

Massachusetts: MassDOT is working with the Town of Carver, Massachusetts to explore the installation of solar arrays on Route 44.

Missouri: MoDOT is using solar power to heat some bridge decks during inclement weather and to provide power to some traffic signals.

New Jersey: NJDOT is retrofitting over 200,000 utility poles with solar panels. It is also looking to install solar panels on the Carneys Rest Area on I‐295 as a part of the national Adopt‐A‐Watt Program.

New York: NYSDOT is considering the installation of solar panels at highway rest areas.

Ohio: Ohio DOT, in partnership with the University of Toledo, created a solar highway along Interstate 280. The arrays were installed in the summer of 2010 and are used to offset electricity use at the Veterans’ Glass City Skyway bridge.

Oregon: ODOT installed the Nation’s first solar highway project in 2008. It is now working to develop other solar power projects along highway ROW.

Washington: WSDOT is considering potential solar installations along Interstates in the state.

Wyoming: Since 1980 WYDOT has opened 19 new rest areas. Solar heating provides nearly half of rest rooms’ energy needs.

WIND ENERGY – DOMESTIC

District of Columbia: DDOT is considering self‐contained turbine street lights but applied research is not underway at this time.

Illinois: Illinois DOT partnered with the University of Illinois to study the feasibility of using wind to provide electrical power at highway rest areas, weigh stations, and team section buildings.

Massachusetts: MassDOT is working to develop a proposed wind turbine project on land adjacent to a Massachusetts Turnpike rest area.

Minnesota: The Minnesota state legislature is currently assessing the benefits and costs of using state‐owned land for wind energy generation systems.

Missouri: MoDOT has two, 1.2 kW wind turbines (one in each traveling direction) installed at a Welcome Center on I‐44 in Conway, Missouri. The wind turbines power the lights over the information counters.

Ohio: Ohio DOT was advancing projects involving the installation of wind turbine electrical generators at two Interstate rest areas (I‐90 in Ashtabula County and I‐75 in Wood County) in order to provide power for these rest areas. The projects, which would have included the installation of Truck Electrification Systems for use at no cost, have been cancelled due to changing priorities.

Washington: WSDOT had been approached with the idea of installing wind turbines on the SR 16 Tacoma Narrows bridge and as part of the I‐5 Columbia River Crossing bridge replacement project, but no specific proposals have been received.

Other: Some consulting firms have indicated intentions to install wind turbines along highway medians in several states. At this time, these claims could not be substantiated. (e.g., the Nebraska Department of Roads (NDOR) has been approached by a company to allow wind turbines in the highway ROW. NDOR is currently investigating whether this use would be permitted.

BIOENERY – DOMESTIC

Kentucky: Kentucky State University conducted a study to calculate the ethanol production potential of ROW along interstates and parkways in Kentucky.

Michigan: MDOT has planted a biocrops test plot along its ROW.

Missouri: The Legislature has approved measures to allow MoDOT to produce switchgrass on the ROW.

North Carolina: NCDOT is currently piloting the use of highway ROW to grow biocrops such as canola and sunflower.

Ohio: Members of the Etna Township Economic Development Committee have advocated for the planting of biocrops along I‐70 in Ohio. www.dispatch.com/live/content/local_news/stories/2010/12/09/money‐making‐pitch‐biofuel‐crops‐along‐i‐70.html?sid=101

Oregon: ODOT jointly submitted a New Special Experimental Project (SEP‐15) application to USDOT with the DOTs in California and Washington for the I‐5 Alternative Fuels Corridor Project. The application/project would allow limited commercialization of highway rest areas to promote the use of alternative fuels. USDOT determined that the concept would be better implemented through modification to the Interstate Oasis Program (www.fhwa.dot.gov/safetealu/factsheets/iop.htm) guidance. A rule change has not been initiated to date.

Tennessee: Tennessee DOT, in conjunction with Genera Energy LLC, a Knoxville‐based renewable energy company, recently planted several test plots of switchgrass along interstate corridors in Tennessee. The plots are designed to assess whether switchgrass can help reduce maintenance costs by reducing the need for mowing and may also have the added benefit of producing biocrops for energy and reducing erosion at highway interchanges.

Utah: Utah State University, in conjunction with Utah DOT, has experimented with growing oil‐seed crops in grassy highway medians and shoulders.

ELECTRIC VEHICLE CHARGING STATIONS – DOMESTIC

District of Columbia: The Sustainability Plan specifically addresses refueling and recharging infrastructure to encourage the use of alternative fuels and advanced vehicles. DDOT launched its Park and Charge Pilot program in November 2010. A recharging station is located in the 2000 block of 14th St., NW and additional stations are planned.

Florida: The Florida Turnpike Enterprise has plans to install recharging stations along the Florida Turnpike, beginning with several stations at the Turkey Lake Service Plaza.

Nevada: NDOT formed an EV task force to look at the potential for adding charging stations operated by a third party on the Interstate or other ROW

Oregon: Oregon is participating in the EV Project. Additionally, ODOT received a $2 million TIGER‐2 grant to support the installation of 20 new EV charging stations along the I‐5 corridor in the northwest part of the state.

Tennessee: TDOT is considering a proposal to place a charging station at a rest area. 

Virginia: Has charging stations at rest areas, installed at no cost to the state. The first stations were installed at the New Kent Safety Rest Area on I‐64.

Washington: WSDOT is currently working to install electric charging stations on I‐5, as part of the West Coast Green Highway. Two rest areas have been identified for installations, one in northern WA and the other in southern WA.

WAVE ENERGY – DOMESTIC

Hawaii: Hawaii DOT is having early discussions regarding installation of a line in the ROW for wave energy transmission.

HYDROGEN – DOMESTIC
California: Caltrans is exploring legislation to allow charging stations at Park and Ride facilities, which the Vehicle Code currently prohibits. The California Hydrogen Highway Network was initiated in 2004 to support and catalyze a rapid transition to a clean, hydrogen transportation economy in California. California has recently awarded funding to develop nine hydrogen stations to support clusters in Los Angeles and San Francisco.
East Coast: Companies have announced plans to build 11 hydrogen fueling stations, each approximately 145 miles apart, from Florida to Maine.
South Carolina: Has public‐private partnership to advance the commercialization of hydrogen fuel cell technologies in SC, including installing hydrogen fueling stations.

OTHER – DOMESTIC

Arizona: Considering testing the use of compressed air technology to store heated energy underground in order to produce electricity. The research site is located on excess ROW at I‐10 and I‐24 street bridges inside the City of Phoenix. The project has been in place for approximately 1 year.

Colorado: CDOT conducted a statewide feasibility study to identify potential renewable energy sites on the state’s highways.

Massachusetts: MassDOT conducted a statewide feasibility study to identify potential renewable energy sites on the state’s highways. 

Minnesota: Minnesota DOT is considering options for sequestering carbon on highway ROW using native vegetation.

North Carolina: NCDOT is building sustainable rest areas that incorporate solar panel and wind turbine technologies in their designs.

Nebraska: In April 2010, FHWA entered into a cooperative agreement with the University of Nebraska‐Lincoln to explore possibilities to incorporate wind and solar hybrid energy harvesting systems with a “microgrid” that manages energy produced with demand from surrounding infrastructure.

Nevada: NDOT is considering installation of a geothermal renewable energy transmission line within the ROW based on an NV Energy permit application.

New Mexico: New Mexico DOT is considering options for sequestering carbon on highway ROW using native vegetation.

Ohio: Ohio DOT had plans to develop green rest areas that are powered by renewable energy and that would include ethanol fueling stations and electric car recharging bays. These plans have been cancelled at present.

Texas: TxDOT and the University of Texas are conducting a research study to develop criteria for assessing ways to extract value from the ROW.

SOLAR ENERGY – INTERNATIONAL

Australia: Installed highway noise barriers made of PV panels.

Austria: Installed highway noise barriers made of PV panels.

Germany: Installed highway noise barriers made of PV panels; has several solar projects including solar arrays installed on highway close to Freiburg and 16,000 solar panels on the roof of a tunnel of A3 highway near Aschaffenburg.

Iraq: Installed solar panel and bulbs along roads to power streetlights.

Italy: Opened the world’s first completely solar highway on January 1, 2011. The roadway situated between the cities of Catania and Syracuse, is 19 miles long and cost $81 million to construct. It integrates a series of PV panels along the entire distance of the roadway that generate enough electricity to power all of the highway’s systems including the lighting and fans inside the tunnels and the highway lighting and emergency phones placed along the stretch of road. The solar panels will generate an estimated 12 million kW of solar power annually. www.energydigital.com/tags/a18‐catania‐siracusa/italians‐race‐solar‐powered‐highway

Japan: Plans to subsidize half the cost of installing solar power generation systems at public facilities, including highway rest areas. 

United Kingdom: PV systems on highways provide electricity to power highway energy signs, lighting and equipment or into the national grid for more general use.

Spain: Has implemented solar car ports.

Switzerland: Installed highway noise barriers made of PV panels.

WIND ENERGY – INTERNATIONAL

France: An experimental wind turbine along the A6 between Paris and Lyon generates 1.5 kW of electricity, enough to power local road signs, speed detectors and video cameras.

Israel: Israel has planned to implement wind‐powered lighting for coastal highways.

Netherlands: The Netherlands has implemented wind turbines along highways A12 and A20.

WAVE ENERGY – INTERNATIONAL

France: Paris authorities are exploring a proposal to install eight turbines underneath bridges to harness energy from currents of the river Seine.

ENERGY HARVESTING – INTERNATIONAL

Italy: Israel’s Innowattech is working to provide renewable energy for highway signs in Italy. Generators are being placed beneath the highway’s upper asphalt layer to capture the electrical charge created from moving vehicles on the road.

Netherlands: Ooms Avenhorn Holding BV has developed a way to siphon solar heat from asphalt road surfaces and use it to de‐ice roads and help power nearby buildings.

South Korea: Researchers are currently designing induction strips and inverters that, when placed in the road, will help recharge passing electric vehicles.

http://green.blogs.nytimes.com/2009/06/10/giving‐new‐meaning‐to‐electric‐avenue/ United Kingdom: Experimenting with pavement heat transfer systems.

HYDROGEN – INTERNATIONAL
Canada: Planning to construct hydrogen highway in British Columbia with seven fueling stations.
European Union (EU): Members of the European Parliament have voted to develop the EU hydrogen highway network system in regard to technological and safety standards among the different countries. Denmark plans to link the Norway HyNor Project with the mainland European nations via its Hydrogen Link project. www.h2moves.eu/regions/sweden_western.html
Iceland: Icelandic Hydrogen is working towards the future hydrogen refueling infrastructure solutions focusing on small‐scale hydrogen refueling stations.
Japan: Installing hydrogen stations along highway in Fukuoka Prefecture. Ten Japanese energy companies including automakers and gas suppliers have announced that they plan to install 100 hydrogen fueling stations in the country by 2015.
Norway: Hydrogen highway spanning nearly 375 miles between Oslo and Stavanger.
South Korea: Operating six hydrogen stations near highway, with others planned.

OTHER – INTERNATIONAL

Finland: Finland is proposing to build the world’s first carbon‐neutral highway. The highway would use a mix of biofuels, EV charging infrastructure, and renewable energy generation technologies. The highway would use EV charging points that obtain their power from solar and wind energy. The project is under the feasibility stage and is projected to be completed by 2016, if passed.

Observations and Findings

Several state transportation agencies are currently working to accommodate renewable energy technologies and alternative fuel facilities in highway ROW. The project team held a series of
telephone interviews with staff from California, Ohio, Oregon, Massachusetts, and North Carolina DOTs and their partner organizations to learn more about the current state of the practice and discuss the challenges faced and lessons learned in doing so. The following section offers a summary of these states’ experiences, focusing on their valuable insights into the issues that may arise and the topics that need to be considered when designing, developing, and implementing highway renewable energy and alternative fuels projects. The findings presented below are based on a synthesis and analysis of insights collected during the interviews and peer exchange convened March 30-31, 2011. Complete case studies are included in Appendix C.

A Supportive Institutional Environment is Critical

The approach to developing renewable energy technology and alternative fuel facility projects in highway ROW will differ from state to state based on the statutory, geographic, climatic,
cultural, and political contexts. A supportive institutional environment is critical for the success of renewable energy projects in the ROW. Many of the projects analyzed in the case studies are
located in states that have strong renewable energy generation and GHG emission reduction goals.54 In the case study examples, state and state agency leadership were receptive to pursuing
renewable energy projects in the ROW as a strategy to meeting the established target and goals. However, even in agencies that are committed to generating renewable energy and reducing its
carbon emissions, securing internal leadership support for these projects typically required a great deal of persistence from a project champion. Renewable energy projects are not typical to
the DOTs’ day-to-day activities; and over the course of the project, challenges and potential obstacles will inevitably arise. In the cases reviewed, a committed project champion was vital in
working with the parties involved to overcome these potential barriers and keep the project moving forward.

Siting Concerns and Requirements for Renewable Energy Projects in Highway ROW are a Principal Issue

Transportation agencies must provide safe and efficient transportation systems for the public; any project in the ROW must not compromise a transportation agency’s ability to meet this
mission. As such, when siting renewable energy projects, project proponents must adequately address specific transportation issues and concerns, primarily safety, as well as reliability,
durability, security, and avoidance of traffic flow disruptions. Criteria that the DOTs and project partners have used to site solar and wind power projects include:
54 For example, MassDOT’s GreenDOT initiative aims to incorporate sustainability into all of its activities; from strategic planning to project design and construction to system operation. The initiative includes GHG reduction targets mandated under the Global Warming Solutions Act, signed by Governor Patrick in 2008. This law requires an 80 percent GHG reduction by 2050.

• Height and set-back requirements. Renewable energy systems in the ROW must be installed in locations that minimize impacts to the traveling public. Acceptable height and setback requirements based on existing constraints will need to be established. These requirements will typically be site specific, and may differ by technology type. Generally, DOTs require that any renewable energy facility in the ROW be located outside the clear zone and/or behind a barrier, such as a guardrail. Wind turbines will typically require larger set-backs to account for the risks of blade flicker,55 falling fragments, or ice being thrown from rotors. CDOT used a 250-foot clear zone in its statewide assessment of potential wind turbine locations while MassDOT’s proposed wind turbine would be set back 1500 feet from the roadway (a large parcel was available so the MassDOT decided to locate the turbine in the middle of the parcel). As a comparison, Caltrans required a 52-foot setback from the travel lanes and the on-ramp for the proposed solar projects in California. The solar panels in Carver, Massachusetts will be set back approximately 60 feet from the roadway, which is also the setback distance of the security fence surrounding ODOT’s solar demonstration project.
• Access. Site access for construction, operations, and maintenance must be designed to avoid public safety and security issues. Ensuring safe access is a primary consideration
  when deciding on appropriate locations to site projects in the ROW. Some factors to consider include direct access from the highway versus local street access to the back of the ROW line; whether acceleration and deceleration lanes will be necessary, if access is from the highway; whether there will be restrictions to a site based on peak hour traffic, season, or other factors.
• Proximity to electrical interconnection and transmission lines. The electricity the renewable energy system(s) generates can feed into the utility grid or directly into a facility. The site must be in close proximity to the grid connection, transmission lines, and/or power user to minimize utility interconnection costs and ensure that the projects can be economically feasible. Unless it is utilized onsite, after electricity is generated it must travel on utility transmission lines to be used elsewhere. There are significant areas of land, particularly those in rural locations where renewable energy production potential may be high, with sparse transmission line coverage. Without transmission line access, production of renewable energy not consumed onsite may be infeasible or costprohibitive.
• Minimum site acreage. The site acreage must be able to accommodate a renewable energy facility that is large enough to make the project economically feasible. DOTs should consider developing criteria for what constitutes adequate acreage (based on the proposed project type). Experts in the renewable energy field may provide valuable insight into minimum site acreages. Site capacity for wind turbines is based on the turbine blade length and the height of the tower. If more than one turbine is planned, the site must be able to accommodate the necessary spacing between wind towers. In the case of solar projects, ODOT and PGE determined from the demonstration project that at least 1 MW needs to be produced to make a solar highway project economically feasible in the state. The organizations have determined that currently about five acres are required to generate that amount of energy. The Ohio DOT also came to the same conclusion that 1 MW, which requires five acres of land, is needed for these projects to be economically viable. This metric will continue to evolve as new solar panels that are higher wattage are becoming available, allowing more energy generation on a smaller footprint.
• Potential future use of the site. A state DOT should evaluate potential sites against the metropolitan and statewide long-range transportation plan to ensure that the site will not
  be needed for another transportation purpose in the future. This would help avoid having to remove the renewable energy system before its operating life is over.
• Proximity to aircraft navigation systems. The form “7460-1 – Notice Of Proposed Construction or Alteration” must be filed with the Federal Aviation Administration
  (FAA) before construction of any structure over 200 feet (i.e., all utility-scale wind turbines). The FAA and the Department of Defense (DOD) review these filings for any potential obstruction or interference with air traffic, aircraft navigation/communication systems, military RADAR, or other systems. Most sites that are not within about 3–5 miles of a public or military airport are not considered a hazard to air traffic.
• High visibility. Many of the interviewed DOTs sought locations for their first renewable energy projects that were highly visible to the public. Locating initial renewable energy
  projects in high-visibility locations can help to raise public awareness of a DOT’s sustainable energy efforts and the associated benefits.
• Availability of natural resource to be used. Maps that show natural resource availability (e.g., solar or wind potential) and/or that estimate the theoretical maximum electricity amounts possible can be helpful for State DOTs in determining locations potentially conducive for a renewable energy system. ROW maps and GIS data layers can be intersected for each renewable resource type (e.g., solar, wind, and biocrop) as a useful energy production estimating tool. Producing biocrops in the highway ROW appears to raise fewer safety issues for transportation
  agencies as compared to solar and wind projects. Safety issues associated with growing biocrops in the ROW are generally the same as they would be for managing existing roadside vegetation. State DOTs would still need to locate areas of biocrop production in ways that minimize potential safety issues involved with harvesting the crops. NCDOT, for example, planted crops 10 feet from the road and included a grass buffer to further separate the crops from the roadway. By planting the crops at that distance from the road, it is not necessary for NCDOT to close a travel lane for a mobile operation of equipment when harvesting the biocrops. Criteria that DOTs have used to assessing locations for bioenergy projects include:
  • Minimum site acreage and slope. Plot sizes are typically 100-foot-wide crop area per mile. The slope of a potential highway ROW biocrop project would affect the ability of roadside maintenance staff to cultivate any biocrops produced. As slopes increase, it may become more difficult for necessary equipment to reach the biocrop to be harvested (equipment can typically handle slopes of up to 35 percent). Steep slopes can also be less stable than lower sloped lands while presenting drainage and erosion challenges. Agencies can utilize GIS tools to analyze slope, width of ROW, and shoulder width sections to identify appropriate locations for biocrop production.
  • Regional climate. Seasonal rainfall and temperatures play important roles in crop selection and resulting yields. For example, Utah’s arid climate was one factor in low crop yields. In contrast, North Carolina’s annual rainfall provided an ideal environment, which contributed to high yields.
  • Soil type. Soil type plays an important role in crop yields. Soils that readily retain water, have high organic matter, and minimal clay content are generally more conducive for
    higher crop yields. However, soils near roadsides are often compacted to a higher degree than traditional farm soils (due to road construction, storage of vehicles and equipment,
    or other uses of heavy equipment), presenting a significant challenge for biocrop production in highway ROW. The soil needs to be loosened in a manner that does not
    impact the stability of the roadway. Research institutions and transportation agencies participating in the Freeways to Fuel program are currently exploring methods to best
    address soil compaction issues over the term of bioenergy projects.
  • Wildlife concerns. When assessing potential highway ROW locations for biocrop projects, ROW practitioners should consider the species of crop to be planted and
    whether it might be expected to attract wildlife near the roadway. Many factors contribute to wildlife-vehicle collisions, and there is little conclusive evidence that addresses
    whether one single variable alone can effectively predict or correlate to wildlife-vehicle collisions. Vegetation management guidance has often focused on the removal of certain
    vegetation species that are attractive to wildlife within the ROW, thereby reducing or eliminating habitat and suggesting a correlation between vegetation and wildlife strikes.56
    On the other hand, some researchers have found that the presence of open land cover, believed by many to improve driver visibility or reaction time, could be correlated to
    increased presence of some wildlife species and, by extension, wildlife-vehicle collisions.57

Projects Can Be Implemented Through a Variety of Public-Private Partnership Models

Although DOTs can appropriate their own funds for developing alternative energy resources within the ROW, the availability of Federal tax credits and potential public-private partnerships
can help to minimize capital and operating costs. Each of the renewable energy projects that the project team examined utilized a different business model, which, in turn, influenced the
permitting process and contracting mechanism involved.

55 Blade flicker is the alternating light intensity that can occur as a turbine’s moving rotors cast shadows on the ground and stationary objects.

56 Lavsund, S. and F. Sandegren. Moose‐Vehicle Relations in Sweden: A Review. Alces, Volume 27, 1991, pp. 118 to 126., and Jaren, V., et al. Moose‐Train Collisions: The Effects of Vegetation Removal with a Cost‐Benefit Analysis. Alces, Volume 27, 1991, pp. 93 to 99.

57 Barnum, Sarah, et al. 2007. Habitat, Highway Features, and Animal‐Vehicle Collision Locations as Indicators or Wildlife Crossing Hotspots.

Solar and Wind Business Models

Developing a “business model” requires innovation and will likely be unique to each project. The four business models used to date for solar and wind energy projects are:

• DOT purchases the renewable energy generated
• DOT does not purchase the renewable energy generated
• DOT acquires renewable energy credits (RECs) for the renewable energy generated
• DOT owns and operates the renewable energy facility

In the first model, the DOT allows a utility or private developer to install and operate a renewable energy facility in the ROW (through a utility permit, airspace lease, or special use permit); and the DOT purchases the electricity produced by the system. This business model involves two contractual agreements, a lease or license agreement, which allows the third-party developer to site the renewable energy facility on DOT land, and a Power Purchase Agreement (PPA). A PPA is a long-term contract between an energy provider and a customer (in this case a DOT) to purchase the renewable energy for a fixed price over the length of the agreement.

Because the PPA clearly defines the revenue stream over the life of the contract, typically 20 to 25 years, it is a central document in helping the PPA provider secure financing for its project.
Investors front the capital development costs for the system in exchange for state and/or Federal tax credits or other renewable energy development incentives, and the fixed-term power
purchase contract with the customer. This model allows the investor to recoup costs along with a modest rate of return over the life of the tax credits (typically five to six years), and further
provides a revenue stream from the energy for the project owner over the life of the project.

ODOT’s Solar Highway Demonstration Project followed this cost-neutral model; ODOT signed a solar license agreement (SLA) with SunWay 1, LLC to install, maintain, and operate a solar
PV system and a PPA with the company to purchase the electrical energy generated by the PV system. Both contracts are for 20 years with options to renew for up to 35 years. In other cases, DOTs might choose not to purchase the electricity that the renewable energy project generates. Instead, the public utility partner or another public agency could use the electricity generated. When the DOT is not using the electricity, the agency may utilize an airspace lease or a special use permit to permit the project. In this model, the DOT leases the site to the third-party and receives rent but would not enter into a PPA. MassDOT’s proposed solar and wind power examples and Caltrans’ proposed solar projects are each following this business model.

In a third business model being explored, the DOT could acquire the RECs associated with the renewable energy generated, but not the electricity. When a renewable energy facility operates, it
creates two products: the electricity that is delivered into the grid and an REC, which represents the environmental attributes of the power produced. One REC is equivalent to 1 MW hour of
electricity generated. The renewable electricity and the REC can be “unbundled” and sold separately. The REC product conveys the attributes and benefits of the renewable electricity, not
the electricity itself; and the electricity that is unbundled from the REC is no longer considered renewable. The user of the renewable energy system’s electrical output cannot make the claim
that it is using renewable electricity unless the user also holds the RECs associated with the electricity.58,59

There are two different market types in which RECs are purchased and sold: compliance and voluntary markets. Compliance markets are created when a state passes a Renewable Portfolio
Standard (RPS) requiring that retail power suppliers obtain a percentage of the electricity it sells from renewable sources. Some states permit compliance with the RPS, in whole or in part,
through the purchase of RECs. Voluntary markets allow public and private entities to purchase RECs to support renewable energy production. The price of an REC is typically higher on the
compliance market than on the voluntary market. ODOT is currently working with PGE on a second solar highway project in which ODOT will receive a portion of the RECs the facility
produces while PGE will retain the electricity. ODOT will enter into a site license agreement with the utility, but it will not be a party in the PPA.60 ODOT will receive a token annual site
license fee, with the idea of creating a framework for future projects with higher fees. By holding a portion of the RECs produced, ODOT will be able to claim them as contributing toward the
agency’s sustainability and carbon reduction goals as defined in the Oregon Transportation Plan and other state policy documents.

In the fourth business model, the DOT would not enter into a public-private partnership but would instead own and operate the system itself. The Ohio DOT followed this business model in
its current solar array and maintenance facility wind turbine. However, the Ohio DOT has determined that owning the renewable energy facilities is not a sustainable business model, as
the cost of alternative energy generating equipment is often high and prohibitive for DOTs. In future projects, Ohio DOT would advocate for a utility or private partner to own and operate the
facilities with Ohio DOT purchasing the renewable energy through a PPA; the DOT plans to hire the services of an “energy broker” professional to help it buy energy in bulk, reducing the per
kW rates. The lower rates could be achieved through tools such as reverse on-line auctions where suppliers bid on the right to supply energy to the DOT. The costs of developing renewable
energy projects can also be lowered if private entities develop them, as they are able to take advantage of tax credits and other incentives, such as accelerated depreciation unavailable to the
DOT. When the DOT fully capitalizes renewable energy projects, the costs can be higher; and the agency is less likely to experience a return of investment over the life of the project.

Bioenergy Business Models

Bioenergy projects also may utilize various business models. In NCDOT’s current model, the DOT grows and cultivates the biocrop feedstock in the ROW and then pays a biorefinery to
convert the feedstock grown into biofuel that the DOT later uses. It has been envisioned that a state DOT could also either sell the feedstock or sell permits to farmers to allow them to grow,
harvest, and then use or sell the biocrops as they desired. Finally, USU evaluated another business model where the DOT performs both the farming and refining functions. It was 58 Center for Resource Solutions. 2010. Best Practices in Public Claims for Solar Photovoltaic Systems.

59 The Federal Trade Commission (FTC) has issued guidelines for the use of environmental marketing claims: www.ftc.gov/bcp/grnrule/guides980427.htm. In October 2010, the FTC issued proposed updates to the environmental marketing claims guidance: www.ftc.gov/os/fedreg/2010/october/101006greenguidesfrn.pdf
60Additional information on state‐driven approaches to financing clean energy projects is available from the National Governors Association Center for Best Practices. See:
www.nga.org/Files/pdf/1101CLEANENERGYFINANCING.PDF

determined that this model was not economically viable since the DOT would have to purchase and operate refining equipment that may already be available and operated more efficiently
locally.

Permitting Processes Vary Based on Project Details

Each of the solar and wind energy cases the project team reviewed utilized a different permitting process to approve the use of the highway ROW: the utility permitting process, an airspace lease,
a special use permit, and an easement.

Oregon’s I-5 solar highway demonstration project was approved under the DOT’s UAP. ODOT, in consultation with the Oregon Department of Justice (DOJ) and the FHWA Division Office
determined that since the project would supply electricity for ODOT’s direct use (thereby a “public” use), the project would be permissible on ODOT’s ROW through the utility permit
process. The proposed Massachusetts projects will utilize airspace lease and easements. (California’s proposed solar highway project would have also utilized an airspace lease). In these
cases, the state DOT is not the end user of the electricity generated by the renewable energy project. Under Federal regulation (23 CFR 710.405), a state DOT may receive fair market
income from airspace leases. MassDOT will require the developer of the wind turbine to pay an annual rental fee for use of the land. The rent will be tied to the total revenue generated by the
facility with the rent equal to 3.5 percent of power sales with a minimum of $15,000 a year.

Similarly, MassDOT is collecting fair market income at the rate of $880 a year from Carver for use of the 1.26 acres of highway ROW for its solar installation. Developing the Lease Agreements is a Multifaceted Process Whether a project is permitted through the utility permit process, airspace lease, or special use permit, the DOT and the project partner will enter in a written agreement that outlines the applicable terms and conditions for the use of the ROW. A DOT must ensure that the written agreement used to permit renewable energy facilities in the ROW is adequate to protect the transportation facility and clearly defines the responsibilities of the parties regardless of the permitting process used. An effective lease agreement must reflect legal, planning,
environmental, design, construction, maintenance, insurance, safety, warranty, and security requirements. Developing a lease agreement that is acceptable to both the DOT and the lessee
can be a complex, lengthy, and expensive process.

The interviewed DOTs identified the following items as some of the major issues that need to be considered in developing a lease agreement for solar and wind facilities:

• Site Security. Security of renewable energy technology and facility investments in highway ROW is a practical concern. To protect roadside equipment from theft or vandalism, project proponents are required to include specific procedures and measures in their plans to mitigate risks. Such measures may include, but are not limited to, security fencing, continuous security monitoring, surveillance cameras and communications equipment, hardening installation (such as the use of one-way screws), and embedding locator devices in equipment.  Maintenance. Renewable energy facilities in the highway ROW require maintenance throughout the construction and operational phases, including the equipment itself as well as the land on which the equipment resides. The agreement for ODOT’s I-5 solar demonstration project assigned maintenance responsibility for the solar project to the licensee while ODOT retains responsibility for maintaining the ROW outside the project area. Similarly, the Town of Carver will be responsible for maintaining the immediate area around the solar power project while MassDOT will retain responsibility to maintain the ROW area beyond the project bounds. DOTs should also consider requiring vendors to provide the DOT with maintenance schedules and all warranty information available for the renewable energy installation and its components.
• Liability. Liability can be a contentious negotiation issue between the DOT and the lessee. The lessee should be required to maintain insurance covering injuries to persons
  or damages to property and the renewable energy system in order to minimize potential risk to the DOT. Additionally, the lease agreement should include indemnification provisions for both the DOT and the lessee. One such indemnification provision should pertain to patents and include language that the lessee must comply with any patents that
  may exist.
• Vacating the site/removing equipment. The lease agreement should outline responsibilities for removing the renewable energy technologies and associated equipment and restoring the site to its pre-installation condition upon expiration or termination of the agreement. DOTs may choose to include a clause providing them the opportunity to purchase the renewable energy system at the end of the contract term.
• Termination. The contracts should outline the process and conditions under which the agreement can be terminated. Reasons for DOTs to terminate a project include public safety or highway safety purposes; to comply with a transportation construction project adopted in an approved state transportation plan or changes in applicable laws requiring use of the licensed area. The contract should outline who is responsible for costs in the event of early termination.
• Ownership of the Renewable Energy Credits. The agreement should clearly state what entity retains ownership of the RECs the renewable energy facility generates. DOTs May Require Outside Assistance in Developing Complex Contract Agreements When a DOT purchases the renewable electricity generated, it typically does so through a PPA. PPAs are complex legal documents that DOTs may not be able to develop given current areas of in-house expertise. Therefore, the DOT may need to utilize outside legal counsel or consultants to help guide the development process of these agreements.

ODOT was the first Oregon state agency to enter into a solar site license agreement or a PPA. Legal staff at ODOT and the state’s DOJ worked with an outside legal team to help draft the
documents. The legal fees associated with developing these agreements constituted a large percentage of the overall project costs for the state. Similarly, the Town of Carver, Massachusetts is utilizing a $50,000 technical assistance grant it received from the Massachusetts Department of Energy Resources’ Energy Efficiency and Conservation Block Grant program to retain consultants to support the town with developing its PPA.

Responsibility for Environmental Clearance Varies by State and Project Type

Renewable energy and alternative fuel facility projects in the highway ROW must meet all applicable Federal and state environmental regulations (e.g., NEPA, Endangered Species Act compliance, etc.). Each of the projects reviewed has conducted or is conducting detailed environmental analyses on common issues such as water quality, air quality, biological and cultural resources impacts, hazardous materials, and noise. However, responsibility for conducting such analysis varied across projects. In the Oregon demonstration project, ODOT was responsible for the environmental analysis and for the costs of mitigating or rehabilitating the impacts. In contrast, in both California and Massachusetts, the project proponents are responsible for complying with the state’s environmental protection regulations.61

Each renewable energy technology also has its own set of unique environmental, health, and safety considerations. According to those interviewed, some of the primary considerations
associated with solar energy projects in highway ROW to date have included:

• Glint and glare. DOTs may be concerned about the potential impacts of glint (increase in brightness) and glare (reflectivity) on traffic safety. Project proponents have addressed
  these concerns by describing how solar panels are designed to absorb sunlight and by citing related technical studies, such as the “Technical Guidance for Evaluating Selected
  Solar Technologies on Airports” that the FAA issued in November 2010.62 The Ohio DOT is also using its solar field demonstration project to evaluate glint and glare impacts.
  Glint and glare have not presented issues for the projects accommodated to date in the ROW.63 DOTs should still consider whether it is necessary to have a provision in the
  agreement that states the developer will mitigate glint and glare issues that may arise on the project in the future.
• Electromagnetic field (EMF) environmental, safety, health, prevention, and control issues. EMFs are electric and magnetic fields associated with electric potential, voltage,
  and currents. While the Federal Government has not established regulations governing exposure to power frequency magnetic fields, the International Commission on Non-
  Ionizing Radiation Protection has developed exposure guidelines in order to protect the general public and workers against potential adverse health effects. The Institute of
  Electrical and Electronics Engineers and the World Health Organization also have voluntary safety and health exposure limits. ODOT addressed citizen concerns about
  potential health effects of EMF by evaluating the sources and scale of the EMFs to be produced by its proposed solar projects. The review found that EMF levels of the
  proposed solar project do not approach the levels considered a risk to human health.64 In

61 The California Environmental Quality Act (CEQA) applies to all discretionary projects proposed to be conducted or approved by a California public agency. The Massachusetts Environmental Policy Act (MEPA) applies to projects that meet certain review thresholds and that require state agency action, i.e. a permit, financial assistance or land transfer from state agencies. 62 FAA’s Technical Guidance for Evaluating Selected Solar Technologies on Airports: www.faa.gov/airports/environmental/policy_guidance/media/airport_solar_guide_print.pdf
63 More information on the potential glare impacts from one of ODOT’s proposed solar highway projects is available at: www.oregon.gov/ODOT/HWY/OIPP/docs/Solar_GlarePotentialWL.pdf
64 Good Company. Scaling Public Concerns of Electromagnetic Fields Produced by Solar Photovoltaic Arrays. www.oregon.gov/ODOT/HWY/OIPP/docs/EMFconcerns.pdf

addition, as part of the project review, NREL conducted a literature review on the topic. Their analysis showed that the magnitude of EMF exposure measured at the perimeter of
PV installations has been shown to be indistinguishable from background EMF and is lower than that from many household appliances.65

Aesthetics. Renewable energy projects should blend in with the highway and the surrounding natural environment and maintain a continuity of visual form without
distracting interruptions. In designing the proposed Caltrans’ solar projects, SMUD worked with a local architect firm to develop preliminary renderings of the installation.
SMUD is also considering working with the local arts commission or having a design competition to generate ideas on how to design the project so that it fits into the
community landscape.

Primary environmental considerations associated with wind energy projects in highway ROW are less apparent than for solar energy projects. DOT experience with wind power technologies
in the ROW has not progressed far enough to have produced lessons learned. According to the literature, one of the primary environmental concerns in wind energy is the potential for bird and
bat mortality; however, impacts vary widely by region and species66; and, overall, some studies have found no evidence of significant impacts on bird populations.67 The Ohio DOT is working
with the U.S. Fish and Wildlife Service to monitor the impacts to birds for its wind turbine project. Additional environmental concerns associated with proposed wind turbines include aesthetics and noise.68

Considerations in the physical environment associated with bioenergy projects in highway ROW are related chiefly to soil and seeding factors. According to those interviewed, environmental
considerations associated with bioenergy projects in highway ROW include:

• Over-cropping and soil health. A DOT might set a threshold for what is an acceptable yield for biocrops planted in the ROW. In efforts to attain that yield, over-cropping and
  loss of soil nutrient health could become issues. Both the Utah and North Carolina projects searched for the appropriate till method to maximize yield without compromising soil health. In North Carolina, this involved examining outcomes from no till, medium-till, and maximum-till approaches. Initially, NCDOT explored the concept of treating all weeds with herbicide and then performing one till; however, test results suggested that the no-till method may be the most effective environmentally and economically. NCDOT also avoided over-cropping and soil health issues by implementing a seasonal crop rotation practice.
• Altered erosion patterns. DOTs considering using highway ROW for biocrop plantings should plant in ways that would not contribute to or exacerbate soil erosion or loss in the
  area.69 Generally, crop rows would often need to be aligned perpendicular to present slopes.
• Cross-pollination. In some instances, the public has raised concerns regarding the potential for biocrops in highway ROW to affect agricultural crop activities and/or reduce
  yields on adjacent farm land. Cross-pollination is a particular concern in areas where seeds or flowers are being commercially propagated (i.e., seed purity is important) near
  proposed roadway biocrop projects.

65 Department of Energy. November 12, 2009. Health effects of electromagnetic fields from solar photovoltaic arrays. www.oregon.gov/ODOT/HWY/OIPP/docs/solar_USDOEmemo.pdf
66 U.S. Government Accountability Office. September 2005. Wind Power: Impacts on Wildlife and Government Responsibilities for Regulating Development and Protecting Wildlife.
www.gao.gov/new.items/d05906.pdf
67 Committee on Environmental Impacts of Wind‐Energy Projects, 2007. Environmental Impacts of Wind‐ Energy Projects.
68 For additional information see www.awea.org/issues/siting/index.cfm.

State and Federal Tax Credits and Grants Are Currently Needed to Make Projects Economically Viable

Renewable projects in the ROW generally rely on public-private partnerships. As a public entity, state transportation agencies cannot benefit directly from Federal or state tax incentives because
they are tax-exempt entities. However, the private partners in these projects can benefit greatly from state and Federal tax credits and grants to finance the renewable energy projects. Renewable energy facilities require high upfront costs. Tax credits and grants help to make renewable energy cost competitive with fossil fuel-based energy. Due to the comparable costs of renewable energy, private partners would likely find renewable energy projects in highway ROW difficult to finance without the availability of Federal and state tax credits. DOTs and project partners indicated that without ARRA funding or available Federal and state tax credits, renewable energy projects in the ROW may not be feasible. Current information on Federal and state incentives for renewable energy can be found at: www.dsireusa.org/incentives/index.cfm?state=us&re=1&EE=1.

Carbon Offsets and RECs Could Be Used to Finance Renewable Resource Development on the Highway System

Carbon offsets enable an organization to reduce its GHG emissions by paying others to undertake activities that reduce, avoid, or sequester GHGs. In the U.S., the voluntary carbon offset market is large and diverse; over 600 organizations develop, market, or sell offsets, and the market involves a wide range of participants, prices, transaction types, and projects.70 The carbon offset markets or the REC markets highlighted above could provide a possible source of funding for renewable energy projects in the ROW. However, involvement in such markets carries with it additional verification and monitoring requirements to ensure the credibility of the offset or REC. Additionally, once the offset or REC is sold, the owner of the renewable energy facility and the user of the associated electricity can no longer claim the renewable energy benefits associated with the project. See www1.eere.energy.gov/femp/pdfs/rec_webinar_062311.pdf for
more information on RECs.

69 For example, see Effective Planting Techniques to Minimize Erosion: Plug Planting, Sod Strips, Hydroseeding, Compost, Jute Netting (2004) by the California Department of Transportation and the California Storm Water Management Program: http://trid.trb.org/view.aspx?id=771549
70 GAO. August 2008. Carbon Offsets: The U.S. Voluntary Market is Growing but Quality Assurance Poses Challenges for Market Participants. www.gao.gov/new.items/d081048.pdf

Patent Issues May Increase Project Costs and Timeline

The systems that produce, collect, and transmit renewable energy are usually patented. Patent holders are entitled to collect license fees for use of the methodologies and techniques their
patents cover. There have been instances where a public entity paid for licenses for a renewable energy technology in the ROW when it was not clear that such licenses were required. This uncertainty, along with the fact that costs are being added to already expensive projects with little or no added value might, be a deterrent to a DOT considering the implementation of renewable energy projects in the ROW. Highway owners are encouraged to consult with a patent or intellectual properties attorney who can help determine the applicability of a particular patent given the legal complexities involved.

Renewable Energy Projects May Require Zoning Changes at the Local Level

Renewable energy projects in the ROW may be subject to local approval and, as a result, may require conditional or special use permits, variances, zoning changes, or waivers in order to meet
regulatory or statutory requirements. For example, the town of Blandford, Massachusetts, in which MassDOT’s proposed wind energy project would be located, does not currently have
zoning standards for wind facilities. Before the proposed project could be approved, the Town first needed to adopt a wind power zoning by-law. In May 2011, registered voters at a Blandford
open town meeting defeated the zoning bylaw that would have allowed the development of the proposed turbine, putting the future of this project in question. The Massachusetts Department of
Energy Resources and Executive Office of Environmental Affairs have developed a model bylaw71 to assist cities and town in establishing reasonable standards for wind development and are
currently working with the town of Blandford to help establish a similar by-law. Similarly, one of the solar projects currently under development in Oregon is located on land zoned exclusively
for farm use; ODOT obtained the necessary conditional use permit from the local jurisdiction without any controversy or appeal.

Renewable Energy Projects Require Effective Public Involvement

Public support of renewable energy development in the ROW is a decisive factor to the success of these projects. Several of the renewable energy projects analyzed as part of this study
conducted extensive public outreach efforts as part of the project development process. For example, as part of the scoping process for the environmental analysis, SMUD held four public
workshops. SMUD had developed visualizations, including conceptual drawings, realistic photo renderings, and 3D animations, to help the public understand what the projects would entail. The
visualizations were used during the public meetings to set the context for each project location and to help generate feedback from the public on the preliminary design. ODOT hired a local
firm to manage the public involvement activities related to its solar demonstration project. The firm was able to conduct research describing when the solar highway would become “carbon
positive,” or beneficial to the atmosphere.72 The research has been an effective public relations tool.

Several of the interviewed DOTs have continued their public involvement efforts after project implementation. PGE and ODOT have created a website where the public can get real-time
information on the amount of electricity being produced at the I-5 demonstration site.73 Ohio DOT maintains a similar project website that displays the total electricity production for its solar
field demonstration project.74 MassDOT would require the selected developer of its proposed wind project to install an information kiosk at the adjacent Blandford Service Area if the turbine
is built. The kiosk would provide a written description of the wind turbine project and real-time information on its operation.

71 Massachusetts Department of Energy Resources. March 2009. Model As‐of‐Right Zoning Ordinance or Bylaw: Allowing Use of Wind Energy Facilities. www.mass.gov/Eoeea/docs/doer/gca/gc‐model‐wind‐bylawmar‐10‐2009.pdf
72 Good Company. August 2008. Avoided Carbon Emissions from Solar Panel Systems and Sequestered Carbon Emissions from Tree Growth  www.oregon.gov/ODOT/HWY/OIPP/docs/treesvsolar.pdf

Conclusions and Recommendations

State DOTs are increasingly recognizing the threats climate change effects pose on transportation infrastructure, as well as the GHG mitigation potential that renewable energy and alternative fuel technologies present. Likewise, many utility companies have established renewable energy goals, often in response to state or regional GHG regulation. Together, DOTs and utility companies are beginning to capitalize on the opportunities that utilizing ROW presents to develop sustainable energy sources. Doing so not only reduces reliance on fossil fuels but can also promote energy security and conservation, and foster the creation of a local green job market. Such uses can also reduce highway maintenance and operational costs (in instances where a partner agency assumes maintenance responsibility) and generate additional revenue for transportation agencies. The following section describes best practices for both DOTs and FHWA to achieve desired outcomes in producing and distributing renewable energy and alternative fuels along the highway ROW, should a DOT decide to do so.

Best Practice Opportunities for DOTs

Use of the highway ROW to develop sustainable energy sources has only recently emerged as a viable solution to reduce the GHG emissions associated with transportation operations. The
lessons that early adopters have learned and best practice recommendations presented below are intended to inform others seeking to pursue similar projects.

Consider revising state UAPs to include renewable energy.

DOTs interested in utilizing the ROW for renewable energy technologies or alternative fuel facilities should be proactive in their approaches to implementing these projects. State DOTs are
encouraged to review their respective UAPs to ensure they are consistent with current needs and that the UAP definition of a utility includes or allows for renewable energy technologies.  Identify state statutory or regulatory constraints that preclude resource development and devise resolutions that would instead foster such development. Attempts to accommodate renewable energy technologies and alternative fuel facilities in the ROW will likely expose legal constraints that limit opportunities for renewable resource development. A state’s utility rules for net metering and feed-in tariffs, for example, may inadvertently and artificially restrict the most promising renewable energy sites on highway ROW. Some rules, such as those in Oregon, only allow consumers to offset load aggregated by meter and feeder across contiguously owned property and on the same rate schedule. Net metering may limit the amount of energy that a given site can generate. These restrictions could result in a greater number of smaller projects, a greater timeline to develop renewable energy resources (or a “solar highway” system), higher cost per kW installed, and/or decisions to pursue REC-based projects instead of those that would be net-metered.

According to some stakeholders interviewed, the development of an “administrative net metering” or feed-in tariff or process would greatly facilitate development of solar power projects in the ROW, ultimately resulting in lowered costs to the public. The tariff would allow an agency to offset its entire electricity load in a given utility’s service area by utilizing the most promising ROW locations to their full capacities. While a state DOT might not necessarily take the lead on this action, its involvement and partnership with other agencies will likely be important.

Identify appropriate renewable energy technologies and potential sites through a statewide or regional feasibility study.

A systematic review of the alternative energy potential of the ROW and real estate holdings can provide agencies with a clear picture of the quantity and quality of alternative energy resources
under its management and can help a DOT prioritize which technologies to pursue. The following geospatial information is helpful in conducting feasibility studies: transportation real estate holdings; ROW information, including width, slope, and directional orientation; proximity to electricity transmission lines; underlying natural resource constraints, such as presence of wetlands or rare species and their habitats; and renewable energy resource maps. Transportation agencies should work collaboratively with partner agencies to collect and develop the geospatial data deemed appropriate. Additionally, transportation agencies should collaborate with utility companies and public utility boards to share data/maps on subsurface utility facilities for any new renewable energy installations. This would mitigate issues when new transportation projects come along and would help outline potential future utility conflicts.

Review long range transportation plans to identify potential siting conflicts or to develop guidelines for how renewable energy and alternative fuel facility projects might be included in statewide transportation planning.
A Transportation Improvement Program (TIP) is a multi-year capital improvement program of transportation projects. Each metropolitan planning area develops a TIP, which is then
incorporated into the statewide transportation improvement program (STIP). Transportation agencies also develop Long Range Transportation Plans (LRTP) that outline the vision for the
region’s or state’s transportation system and services.75 In metropolitan areas, the LRTP indicates all of the transportation improvements scheduled for funding over the next 20 years.
The Statewide LRTP may not be project specific, but will clearly detail the policy direction the State plans to take over the next 20 years.

The typical length of lease agreements (20 to 25 years) between the DOT and the utility/developer of the renewable energy project corresponds to the planning horizon of LRTPs.
State DOTs should evaluate proposed renewable energy facilities for compatibility against metropolitan and statewide long range transportation plans and TIPs to determine whether
proposed facilities conflict with future expansion of the transportation system or policy direction of the State or metropolitan region.

DOTs that are considering how renewable energy projects could be accommodated in highway ROW should integrate these considerations into the transportation planning processes at the
state, regional, and corridor levels. This integration would enable states to address renewable energy projects in the ROW in a systematic process rather than on a case-by-case basis.
75 For more information on the LRTP process, see www.planning.dot.gov/documents/briefingbook/bbook.htm

Develop an internal interdisciplinary team to address the unique issues renewable energy projects in the ROW present.

Renewable energy projects in the ROW differ from typical transportation projects in many ways. As such, these projects inevitably raise unique issues that standard operating procedures and
policies may not address. Working through such issues requires a great deal of coordination and communication between departments within the DOT, including real estate services, maintenance, operations, safety, environment, planning and legal. It is important for representatives from each of the relevant departments to be involved early in the planning and decision-making process particularly for initial projects, when there is little to no precedent to rely upon. Developing a consistent internal message within the DOT is also an important factor in minimizing delays that can occur when different DOT offices have varying views or give conflicting direction to project partners. One DOT noted that having top management support that set a clear direction for all of the offices regarding the renewable energy project was “hugely beneficial” because it helped to eliminate any reluctance that may have existed. Furthermore, it is important for project sponsors to include a representative from the FHWA Division Office in these early to minimize the potential for delays.

Flexibility and creativity on the part of the DOT and its partners is necessary to devise solutions that meet the needs of all those involved. For example, DOTs might consider creating a full-time
“energy manager” position when feasible. This person would serve as the primary lead and would be responsible for coordinating with the appropriate departments. Several DOTs that were interviewed indicated that the renewable energy learning curve for transportation agency staff is steep and that the dedicated attention of at least one staff member will contribute significantly to the DOT being able to implement a successful project, regardless of the success measure(s) chosen.

The approach to develop renewable energy projects in the ROW is largely dependent upon the specific context of the project, including the ownership and funding structure involved. At this
time, there is no one definitive way to design and develop these projects. Similarly, the success of these projects can be defined in a number of ways including meeting policy objectives, having
cost-neutral or positive return on investment, and level of public acceptance, among others. Even within a state, the model and approach followed may differ from project to project. A prototype
model may emerge as DOTs’ experiences in implementing renewable energy projects in the ROW evolve. Until then, however, DOTs and their partners will need to be flexible and creative
when contemplating, implementing, and evaluating renewable energy and alternative fuel projects.

Create partnerships with external stakeholders.

It can be beneficial for DOTs to build partnerships with external stakeholders, such as utilities, public utility boards, banks, private energy developers, and alternative energy vendors. Building
such relationships that avoid conflict of interest issues can be a valuable asset in educating the DOT and in facilitating issues that may arise later in project development and design. For
example, Ohio DOT staff spoke with numerous stakeholders in the renewable energy field to learn about the technologies available and to ensure that the agency was obtaining the best value
for its investments. The staff attended trade shows where they were able to network with representatives in the renewable energy industry.

State DOTs should also explore opportunities for public-private partnerships, especially in states where capital funding, and thus the means to undertake their own feasibility studies or renewable
energy projects, is limited. Additionally, it is important to coordinate with the utility company early in the development of renewable energy projects where the local utility is not an active
partner. This is particularly important if a proposed project does not have an identified customer for the electricity that will be produced.76

Specifically regarding wind energy project development, wind project proponents should first consult with the FAA, the Joint Program Office (JPO), and any local DOD installations about the
siting of their project in order to avoid delays and unnecessary investigation expense. This should be a preliminary step in the development process. Early consultation with the FAA and JPO will allow project developers to evaluate whether their project site may potentially interfere with air defense radar and determine whether mitigation is necessary and possible. Develop comprehensive value-based selection criteria for renewable energy and alternative fuel facility projects in highway ROW.

Renewable energy projects in the ROW can help agencies achieve their environmental and sustainability goals.

When cost is the primary selection criteria used to award contracts, state-sponsored renewable energy projects could reward labor and environmental practices that are not in line with the overall sustainability and environmental goals that the project is intended to support. Outsourcing jobs and subsidizing such environmental practices may be unintended but foreseeable consequences of solely cost-based public investments. As a result, some states have utilized comprehensive value-based criteria to evaluate and award contracts for renewable energy projects. A state DOT may not necessarily take the lead on this action. Other agencies within a state may develop value-based selection criteria that the DOT could adapt to its needs. When procuring the PV modules for its solar demonstration project, ODOT evaluated proposals using a set of value-based selection criteria (see Appendix E). In addition to corporate qualifications, technical characteristics of the proposed PV modules, and price, the selection criteria also included commitment to Oregon’s Sustainability Policies, such as recycling of PV module materials after their useful life and the manufacturing locations of the PV modules.

Careful consideration of the project’s contribution to the state’s overall public interests and values, not just direct costs, ensured that the demonstration project truly supported the state’s
sustainability goals.

Opportunities for FHWA

There are considerable economic, ecological, legal, and political uncertainties related to whether accommodating renewable energy technologies and alternative fuel facilities can be practical
highway land management practices. FHWA is positioned to provide information and other assistance to DOTs that will better enable them to consider the implications and evaluate the
feasibility of implementing renewable energy and fuel options in the ROW. Based on discussions 76 Organizations such as the Electric Power Research Institute may be able to work with DOTs and FHWA Division Offices to identify utility partners to buy or distribute power.

59 with the stakeholders, FHWA will carefully consider the following next steps, although no commitments are made at this time:

Clarify its endorsement of using highway ROW to accommodate renewable energy technologies and alternative fuel facilities.

FHWA should make its position on accommodating renewable energy technologies and alternative fuel facilities in the ROW clear either in a policy, a directive, or a leadership statement. This activity would help establish continuity in decision-making when key personnel change. FHWA should also establish a point person within FHWA Headquarters whom Division Office staff can contact regarding alternative uses of the ROW.

Consider using pilot projects to identify any needed revisions or policies that restrict a DOT’s ability to construct and operate renewable energy technologies and alternative fuel facilities in
highway ROW.

Commercialization along the interstate highway system is restricted by Federal statute and regulation. States that receive Federal Interstate funding are prohibited from locating automotive
service stations on the ROW of the Interstate System (23 USC 111). States are also prohibited from charging the public for goods and services at safety rest areas except for telephone and
vending machines (23 CFR 752.5). Such restrictions limit the ability of the DOT to construct alternative fuel facilities in the highway ROW. FHWA should consider reviewing these
regulations, perhaps in the context of a pilot project, to determine whether and how the regulations might be modified to better enable DOTs to accommodate alternative fuel facilities.
FHWA should also ensure that new policies do not contradict existing policies and vice versa.

Such activities would align with the January 2011 Executive Order to Improve Regulation and Regulatory Review, which encourages agencies to choose alternative regulatory approaches that
maximize net benefits, including potential economic, environmental, public health and safety, and other benefits.

This action would likely be especially helpful for state DOTs considering highway ROW for siting EV and PHEV charging stations. Although most EV and PHEV owners will likely recharge their cars overnight at home, “range anxiety” among drivers is expected to remain a challenge until the connectivity of the charging network is improved. The ChargePoint America program, funded in part with a $15 million grant from the DOE, is working to address this issue to a degree through its plans to install 4,600 charging stations across the country. However, this and other similar and complementary efforts are necessary to help ensure the use of this potentially cleaner fuel source is maximized. Highway ROW may offer additional suitable locations, assuming regulatory barriers are addressed.

Finally, Federal regulations require that property purchased with Federal Highway funds must benefit the transportation system. This qualification may be an impediment to accommodating renewable energy and alternative fuel technologies in the ROW, particularly in situations where the DOT will not purchase the electricity generated by the renewable energy facility. FHWA should examine whether renewable energy activities within highway ROW could constitute a transportation use and, thus, be eligible for accommodation; the Agency should define or clarify how these activities are connected to the agency’s responsibility to build and finance transportation infrastructure that supports the traveling public’s needs. FHWA should also
reconsider its environmental guidelines and scope of ROW acquisition for future projects, if renewable energy actions are considered authorized transportation uses. This would enable
DOTs to routinely analyze future projects regarding their potential for renewable energy activities. Accordingly, there may be justification to acquire additional ROW to accommodate
the energy purposes along with the highway use. The proposed activity may require revision to Title 23 U.S.C. and Title 23 CFR.

Work with AASHTO and other relevant partners to address patent issues for renewable energy projects in highway ROW.

Some existing patents could be detrimental to advancing the practice of accommodating renewable energy systems on highway ROW. Since it is unlikely that all utility companies will
have necessary licenses, the geographic extent in which DOTs might install projects could be limited. For example, if only one utility company has a required license, that state’s DOT might
be reluctant to consider other solar projects in places outside of the licensed utility’s service area. Presumably, some of the “avoided” regions could have the state’s prime solar, wind, or
geothermal resources and/or available ROW. FHWA should coordinate with AASHTO and other relevant partners to discuss potential patent issues that may exist related to implementing
renewable energy systems in the ROW.

Coordinate early involvement with the U.S. Department of Energy to facilitate the development of renewable energy projects in the highway ROW.

FHWA should facilitate national-level coordination with the DOE to coordinate initiatives and funding in order to maximize Federal support of these projects. Because of the dual energy and
transportation aspects of siting renewable energy projects in the highway ROW, both DOE and FHWA may frequently be involved in the NEPA process. Because each agency has different
processes for carrying out its NEPA responsibilities, determining which agency will serve as the lead agency for NEPA will have implications for projects.77 For example, because ODOT
received funding from the DOE for its Baldock project, the project was initially required to follow the DOE’s NEPA regulations. However, lacking familiarity and experience with DOE’s
NEPA regulations, ODOT requested that it be allowed to follow FHWA’s NEPA regulations. After a lengthy process, DOE allowed ODOT to follow FHWA NEPA regulations for research
and development projects but did not extend the allowance to any potential future renewable energy projects. Similarly, the Ohio DOT essentially completed two NEPA processes, one for
DOE and one for FHWA, for its wind project.

FHWA and DOE should coordinate to address the dual nature of these projects. Developing a memorandum of understanding or other agreement that clearly defines NEPA responsibility for
renewable energy projects in the highway ROW would help to address DOTs’ questions and concerns in this area. Additionally, because such projects support national energy and 77 In 1978, the CEQ issued Regulations for Implementing the Procedural Provisions of the National Environmental Policy Act (40 CFR §§ 1500–1508) to assist Federal agencies in effectively implementing the
environmental policy and “action forcing” provisions of NEPA (42 U.S.C. 4321). To address the NEPA responsibilities that CEQ established, FHWA issued regulations (23 CFR § 771), Environmental Impact and Related Procedures. The FHWA guidance complementing the regulations was issued in the form of a Technical Advisory (T.6640.8a), Guidance for Preparing and Processing Environmental and Section 4(f) Documents. The Technical Advisory provides detailed information on the contents and processing of environmental documents. The DOE’s NEPA implementing procedures are described in 10 CFR 1021.

61transportation goals, the two agencies should work together to leverage funding. Coordinating programs that support climate change, renewable resource development, electric vehicles, smart
grid technologies, and sustainable transportation could enhance the value of each.

Evaluate the benefits of comprehensive value-based selection criteria for renewable energy and alternative fuel facility projects in highway ROW.

Procurement policies focused only on cost-based principles may fail to achieve the values Federal and state leadership has established. FHWA should research effective value-based
selection criteria that DOTs can utilize when awarding contracts for renewable energy and alternative fuel facilities. FHWA could solidify its position as a leader in promoting a more
sustainable transportation infrastructure development practice by assisting DOTs in developing comprehensive value-based selection criteria for renewable energy projects in highway ROW.
Analyze effective DOT practices in administering ROW access on routes controlled under the Highway Beautification Program.

FHWA has issued policy regarding the clearance of vegetation within the ROW that may be impairing the view of outdoor advertising signs from the travelled way.78 Some DOTs have had
experience in allowing contractors ROW access on routes controlled under the Highway Beautification Program for this purpose. An analysis of experiences administering this type of
program could relate to establishing and maintaining renewable energy or alternative fuel uses within highway ROW.

Consider the potential benefits of sponsoring research to evaluate rest areas and/or excess lands for renewable energy generation. 

To date, there has been limited nationwide research on sustainable rest area design and operating practice or their environmental impact or carbon footprints. According to FHWA, the last exact
count of rest areas occurred in 1972, when 1,214 rest areas were reported. A preliminary count made as a part of the research reported here indicates that there may be significantly more rest
areas today. These facilities seem to offer some of the more immediate opportunities for accommodating renewable energy technologies and alternative fuel facilities in highway ROW
given the facilities’ potential sizes, setback from high-speed moving traffic, electricity needs, and potential electricity demands should EVs penetrate the fleet to a higher degree.

The proposed research should analyze available information for rest areas, such as square footage, date of construction, type of construction, use, and proximity to communications towers or other significant interferences and major electrical transmission lines that could provide convenient interconnections to the electricity grid. The analysis would result in development of a suitable site profile or guidance for different scales of renewable energy projects at rest areas.

The site profile or guidance would be based upon a set of criteria that could include minimum requirements for natural resource availability; site acreage; distance from travel lanes, residences, and other development; construction access; and electrical interconnection points’ as well as environmental and other pertinent constraints. The research would potentially help DOTs reduce life cycle cost for energy, conceptualize sustainable and renewable actions and features to rest areas, improve the visitor experience, and reduce GHG emissions.

78 www.fhwa.dot.gov/realestate/oacprog.htm#VEGETATE

Furthermore, previous FHWA ROW acquisition policy encouraged excess ROW acquisition to extend to natural topographical barriers or whole block acquisitions to mitigate environmental
impacts, areas that may be located within or outside the typical ROW limits. According to the questionnaire distributed to FHWA Division Offices as a part of this research, 23 of the 39
respondents indicated that their excess ROW could potentially be used for renewable energy facilities. Alluding to a gap in state DOT property management tracking that has been noted
elsewhere,79 Ohio and Oregon DOTs noted that they are undertaking GIS efforts to identify excess land parcels that are greater than five acres. The DOTs have found that at this time land
parcels at least that size are needed to build renewable energy facilities at scales that make them economically feasible.
Other areas that may be suitable for renewable energy activities because of land use planning changes include scenic easements under the Highway Beautification program, state-owned
borrow pits, waste areas, and banked mitigation lands. Such lands should also be inventoried and included in the assessment of DOT held property interests to help DOTs assess the magnitude of
ROW they may have available for alternative uses.

Help build a community of practice that develops and provides training to ROW practitioners on accommodating alternative energy technologies and alternative fuel facilities in the ROW.
Technology and information transfer will be critical to helping transportation audiences in the future with renewable energy and alternative fuel resource development efforts they may
envision. As such, FHWA should work with relevant partners to help build a community of practice that would be able to develop and provide training on accommodating alternative energy technologies and alternative fuel facilities in the ROW. The proposed community of practice would offer forums (deployed via in-person training courses and/or webinar presentations) for transportation practitioners to share challenges and lessons learned, as well as to ask questions of other DOTs, utilities, universities, and related stakeholders that have more experience. By undertaking this activity, FHWA could also help respective state DOTs establish champions for pursuing renewable energy and alternative fuel projects in the ROW should the DOT desire to do so.

Some strategic training topics that the community of practice should address include:

• Structuring public-private partnerships to support renewable energy projects
• Developing effective lease agreements and PPAs
• Developing a research plan to facilitate the implementation of renewable energy and alternative fuel projects in the ROW.

Potential next steps for FHWA are:

• Present research results on a webinar, or series of webinars, within three months of finalizing the report
• Identify other Federal partners that provide renewable energy training or with whom training curricula on critical topics pertaining to the development of renewable energy projects could be developed
• Develop a detailed action plan for moving forward, including coordination activities with
  DOE.

79 FHWA. 2010. Estimated Land for Carbon Sequestration in the National Highway System. www.fhwa.dot.gov/hep/climate/carbon_sequestration/index.htm and alternative fuel projects in highway ROW

Appendix A: Participant List

Agency	Name
Vermont Agency of Transportation	Daniel D. Dutcher
Georgia DOT The Ray The Ray	John Hibbard Allie Kelly Harriet Langford
Texas DOT	Beverly West
Maryland DOT	Laura Rogers
Minnesota DOT	Ryan Gaulke
Massachusetts DOT	Lily Oliver Donald Pettey
FHWA Headquarters	Tina Hodges Rosemary Jones
FHWA Massachusetts Division	Nelson Hoffman Tomasz Janikula Jason Dvelis Joshua Grzegorzewski
USDOT Volpe Center	Amy Plovnick Carson Poe Mike Scarpino

Appendix B: Agenda

FHWA Renewable Energy in Highway Rights of Way Peer Exchange

July 11–12, 2017

AGENDA

U.S. DOT Volpe Center, 55 Broadway, Cambridge, MA 02142

Room: 2-1-20

Objective: Meaningful exchange among practitioners on issues and approaches for accommodating renewable energy technologies in highway rights-of-way.	Goals: Increased awareness of current practice and considerations related to accommodating renewable energy technologies in highway rights-of-way; enhanced community of practice.

MnDOT begins installing electronic vehicle charging station signs on Interstate 94

ST. PAUL, Minn. – Motorists traveling north of St. Cloud on Interstate 94 will see new “Electric Vehicle Charging Stations” highway signs along their route to indicate there is a network of public, fast-charging stations for electric vehicles nearby. This is the first of many electric vehicle charging stations signs that motorists will see along I-94 as the Fixing America’s Surface Transportation Act is implemented.

“MnDOT is excited to be a partner to promote and educate the public about zero emissions and the electric vehicle charging infrastructure,” said Charlie Zelle, Minnesota Department of Transportation commissioner. “We believe that alternate fuels and electric vehicles will be an important part of the future of transportation and can support progress towards the state’s GHG reduction targets”

In 2016, the Federal Highway Administration selected I-94 from Port Huron, Mich., to the Minnesota/North Dakota border as one of 55 designated routes to promote alternative fuels and help drivers find vehicle charging stations nationwide.

This new network spans 35 states and covers 85,000 miles, and was created under the 2016 FAST Act. The alternative fuel corridors will be used to promote electric, hydrogen, propane and natural gas vehicles by encouraging development of fueling and charging stations along these routes.

MnDOT, in a partnership with the Minnesota Pollution Control Agency, submitted an application to designate I-94 as a ‘Zero Emissions Corridor,’ a type of alternative fuel corridor, to promote the electric vehicle charging infrastructure. Since the designation was announced, MnDOT led coordination with state departments of transportation from Minnesota, Wisconsin, Illinois, Indiana, Michigan, and the city of Detroit on a Memorandum of Understanding to re-brand this section of I-94 as the “Great Lakes Zero Emission Corridor.”

“The leading source of U.S. greenhouse gas emissions is transportation-related,” Zelle said. “We can reduce transportation emissions by supporting lower emission vehicles and alternative fuel corridors. By identifying where fueling stations can be found, we can increase the use of electric vehicles and improve air quality and meet the needs of current and future motorists.”

For a complete list of alternative fuel corridors, visit the FHWA website.

Photovoltaic Noise Barriers

Highway photovoltaic noise barriers (PVNBs) represent the combination of noise barrier systems and photovoltaic systems in order to mitigate traffic noise while simultaneously producing renewable energy. First deployed in Switzerland in 1989, PVNBs are now found in several countries where transportation agencies have sought ways to find multiple uses of their infrastructure. The PVNB experience documented in literature and supplemented through a series of interviews provides evidence suggesting that noise barriers can be designed to produce renewable energy without compromising their abilities to reduce noise, and do so safely. The business case for a PVNB often hinges on the availability of subsidies or other incentives that promote the renewable energy market. Although the first highway PVNB is yet to be constructed domestically, at least two State Departments of Transportation are currently working with partners to pursue PVNB pilots in the United States. Given the substantial extent of noise barriers in the country, the potential for solar energy production on American noise barriers is likely at least 400 Gigawatt hours annually, roughly equivalent to the annual electricity use of 37,000 homes, and perhaps much higher.

Highway Renewable Energy: Photovoltaic Noise Barriers

Contents

• Executive Summary
• 1. Introduction
  • 1.1 Photovoltaic Noise Barriers: The Concept
• 2. Literature Review
• 3. Examples from the International Experience
  • 3.1 Switzerland
  • 3.2 Germany
  • 3.3 The Netherlands
  • 3.4 Australia
• 4. Potential PVNB Projects in the United States
  • 4.1 Highway Noise Governance
  • 4.2 Massachusetts DOT’s Lexington Solar Retrofit Pilot Program
  • 4.3 The Ray: A Potential Testing Ground for Prototype Solar Noise Barriers
• 5. Conclusions
  • 5.1 Lessons Learned Summary
• Bibliography
• Appendix A: Points of Contact
• Appendix B: Interview guide
• Appendix C: Calculations

Executive Summary

Photovoltaic noise barriers (PVNBs) represent the combination of noise barrier systems and photovoltaic (PV) systems. Noise barriers are physical obstructions designed to lower noise levels between noise sources and sensitive receptors, such as hospitals, schools, and residential areas. Photovoltaic systems use solar cells to convert light energy directly into electricity. First deployed in Switzerland in 1989, PVNBs are now found in several countries where transportation agencies have sought to abate noise and produce renewable energy simultaneously.

The literature on PVNBs, most of which is several years old, generally agrees that there is great potential to use both existing and planned new noise barriers to produce solar power. Professionals from select transportation agencies who provided information to the project team echoed these views, especially when the integration of solar technologies is part of a holistic approach to design and construction. According to information collected, noise barriers can be designed to produce power without compromising their abilities to safely reduce noise, and in some cases may improve their performance. The business case for a PVNB is often contingent on the difference between marginal costs of constructing the infrastructure with and without energy generating capacity. Transportation agencies in countries with attractive subsidies or other incentives available to promote the renewable energy market will likely find PVNB implementation more feasible and economically self-sustaining than agencies in countries where the regulatory environment is not as favorable to renewable energy developers.

Although the first highway PVNB is yet to be constructed in the United States, at least two State Departments of Transportation are currently working with partners to pursue PVNB pilots on highways in the United States. Given the substantial extent of noise barriers in the U.S. (nearly 3,000 linear miles), coarse estimates done as a part of this study suggest that the potential for solar energy production on American noise barriers is at least 400 Gigawatt hours (GWh) annually, roughly equivalent to the annual electricity use of 37,000 homes, and perhaps much higher.

Conclusions

In 1999, researchers quantified the technical potential of existing and planned highway noise barriers in Europe to produce renewable energy. ³³ Data suggested peak capacity along roadways in 6 countries to be 580 MWp (~ 200 Wp per linear meter) and that a total of nearly 500 Gigawatt hours per year (GWh/yr) of renewable energy was possible. Extrapolating from these figures and FHWA’s noise barrier inventory, the technical potential³⁴ for generating capacity along highway noise barriers in the U.S. is estimated to be on the order of at least 500 MWp and the renewable energy possibly delivered to be likely at least 400 GWh/yr. The latter is roughly equivalent to the annual electricity use of 37,000 homes (see Appendix C for calculations).

These are likely conservative approximations given that they only account for existing noise barriers constructed before December 31, 2013, and they only account for noise barriers made of select materials: berm only, concrete, concrete precast, concrete block, concrete cast-in-place, and combination berm/concrete. Over 45 percent (1,200 miles or 1,900 km) of noise barriers in the U.S. are made of other materials. This should not suggest, however, that noise barriers that are not berm or concrete cannot integrate PV modules. Additionally, the efficiencies of solar panel technologies have improved over time. State-specific estimates may vary considerably due to factors such as latitude and solar irradiance, noise barrier orientation and PV placement, and topography.

In general, large surface areas are necessary to generate electricity from PV modules.³⁵ Noise barriers offer surface area additional to land and rooftops to accommodate PVs and can provide better land utilization ratios for energy production than conventional solar PV farms.³⁶ Nevertheless, although PVNBs provide for the multiple use of road space, deciding whether to implement a PVNB in a highway setting is not based simply on renewable energy potential or performance. Rather, State DOTs will likely need to employ a holistic planning approach that balances broad view concepts, such as land use and sustainability goals, with site-specific details, such as safety, maintenance needs, and noise mitigation. While other sites, such as rooftops, may be more efficient than noise barriers from an energy generation perspective, transportation agencies should consider assessing their noise barriers for PV opportunities in conjunction with their other properties given the numerous potential benefits of PVNBs. 

Lessons Learned Summary

The case studies of existing PVNBs in Europe and planned PVNBs in the United States provide several insights for transportation agencies interested in implementing PVNBs. The following table summarizes key lessons learned.

PVNB technology	PV modules have been both deployed as retrofits to existing noise barriers and integrated into new noise barriers. Bifacial solar cells, which allow light to enter and be absorbed on both sides, are being used in Europe. These panels provide an advantage in that they can be used in any orientation. Other potential PVNB technologies include thin film solar cells, concentrating PV cells along the periphery of noise barriers, and luminescent solar concentrators.
Financial feasibility	The financial feasibility of PVNBs is highly dependent on the price of the PV panels, the price of electricity, and government incentives for renewable energy (such as net metering, feed-in tariffs, or tax credits) – all of which vary depending on the location and policy context. In the United States, organizations that implement PVNBs may be able to take advantage of statewide renewable energy credit programs, which are used to track progress towards meeting renewable portfolio standards, or net metering policies, which allow solar panel owners to sell excess energy back to the grid.37 At the Federal level, the Solar Investment Tax Credit (ITC) provides a 30 percent tax credit claimed against the tax liability of residential, commercial, and utility investors in solar energy property (note that public entities such as State DOTs cannot directly take advantage of the ITC, since they have no tax liability). Many PVNB projects have been structured as public private partnerships where a developer takes on the construction and maintenance of the PVNB. This arrangement allows States to install solar panels with no upfront costs, allows the developer to take advantage of incentives that the State DOT may not be able to access, and provides the State with a long-term source of electricity, often at a fixed, guaranteed price.
Noise characteristics	Typically, the noise abatement characteristics of noise barriers have not significantly changed after being retrofit with PV modules, and new PVNBs can be designed to adhere to all relevant noise requirements. Since, PVNBs are primarily noise barriers with the added functionality of generating electricity it is important to measure noise levels before and after the installation of the PV to ensure that desired and required noise attenuation is achieved.
Safety	There is little to no evidence to date that PVNBs significantly affect driver safety. Driver distraction and glare can be minimized by locating the PV modules high on noise barriers and/or set back from the roadway, and by ensuring that the panels are at proper angles to minimize glare. PVNBs with a vertical design, such as the Australian PVNB, have not been shown to create glare. Additionally, solar panels are designed to absorb rather than reflect light. PVNBs are not expected to cause crashes if located behind a guard rail(s) or beyond the clear zone.
Maintenance	Several international examples have shown that existing PVNB technologies have minimal maintenance needs. In Germany, the PV panels are not typically cleaned, because the cost of doing so would outweigh any potential efficiency gains. In Australia, the vertical orientation of the PVNB minimizes accumulated dirt on the panels.

---

33 Goetzberger et al. (1999).

34 “Technical potential” in this case assumes that all existing noise barriers made of the materials in the bulleted list will be upgraded with PV.

35 The National Renewable Energy Laboratory has estimated approximately 181 m2 of land area is required for PV per person to meet U.S. energy demands. http://www.sciencedirect.com/science/article/pii/S0301421508002796?via%3Dihub.

36 Wadhawan and Pearce (2017).

37 For information about state solar incentives, see the Database of State Incentives for Renewables & Efficiency at www.dsireusa.org/