In a Commuting Utopia, Efficient Housing Location Could Cut Travel by One-Third

Posted on , SSTI, by Saumya Jain

Most states and local governments are either interested in defining vehicle miles traveled (VMT) reduction goals or already have these in place and are actively working toward VMT reduction. Often these goals are approached either by promoting alternative travel modes or through policy incentives. In a recent article, Canadian researchers ran an optimization model to assess the potential impact of household relocation on home-based travel to work and study destinations. While this is a hypothetical analysis, the results are compelling.

Using data from the 2013 Montreal travel survey of 79,000 households, the researchers designed an optimization model that swaps locations of similar types of households to bring residents closer to their work and study destinations. The model predicts that eliminating the spatial mismatch in Montreal could reduce VMT by up to 38% (8-9 daily miles per household). The results from this analysis also show that:

If the mode choice remains constant despite the new trip conditions following the household relocations, the total mileage for work and study trips would decrease by 42.8% for car drivers, by 35.2% for car passengers, by 13.3% for school bus, and 34.2% for public transport. As a result of the household relocations, walking and cycling latent trips increased, respectively, from 2.6% to 15.5% and 26.1% to 39.9% of motorized trips.

To achieve these stark results, the model relocated 98.2 percent of the total households. Although structural changes as huge as this are not practical, the study  highlights inefficiencies within our current residential distribution. It also emphasizes the importance of housing location with respect to a resident’s travel behavior.

While transportation demand management efforts are successful in inducing sustainable travel choices,  the study indicates it is also important to make relocating closer to work an attractive option. Transit oriented development, new urbanism principles, and infill development are different development strategies that planners and policy makers could use for eliminating spatial mismatch.

SSTI recently published a report with the City of Eau Claire, Wisconsin, highlighting the accessibility and health related benefits of infill development.


“Travel budget” Needed to Meet Climate Goals

Posted on 

By Rayla Bellis

The transportation sector currently accounts for the largest share of carbon emissions in the U.S., so averting climate change will require the U.S. to drastically reduce transportation emissions. A recent study looked at what it would take to meet the U.S.’s carbon reduction target of 80% or greater for passenger vehicle travel by midcentury. The study found that even with a high level of electric vehicle adoption, the U.S. will need to stay within a “travel budget,” or maximum total miles of vehicle travel, to meet existing climate targets.

As the researchers note, the transportation sector is in the early stages of several significant interconnected transitions, including eventual widespread adoption of electric vehicles (EVs), autonomous vehicles, and evolving shared mobility options. These transitions have the potential to impact travel demand, energy use, and emissions in uncertain ways. However, there are some constraints to that uncertainty—for example, EV adoption is limited by how quickly people purchase new cars, so even in an optimistic scenario it will take time for the fleet to fully turn over. EVs currently remain a small percentage of both new sales (2.2%) and the total fleet of vehicles (0.43%).

Using those constraints to limit possible scenarios, the authors examined the requirements for meeting carbon reduction targets by modeling the changes needed in vehicle electrification, the carbon intensity of electricity, and travel demand. They found that if U.S. VMT stays at current levels (about 3 trillion vehicle miles per year), reducing carbon emissions from passenger vehicles by 80 to 90% will require 1) reducing the carbon intensity of electricity generation to essentially zero so that EVs aren’t contributing to emissions, and 2) electrifying 67% to 84% of travel by midcentury.

They also found that we will need to keep total miles of travel within a maximum travel budget to meet our targets at any realistic scale of EV adoption in the U.S. The more we drive, the greater EV adoption will need to be. For example, if we can reduce VMT to 1991 levels (about 2 trillion miles), we will only need to electrify 45% to 48% of travel to meet an 80 percent emissions reduction target. If VMT increases to 4 trillion, meeting that 80 percent target will require electrifying 73% to 79% of travel. The authors suggest that meeting emissions goals will require greater emphasis on policies to reduce total travel demand, including local policies around land use and housing, walkability and community design, and parking.