Compared to the median VMT of 19.2 miles per day, employees who were offered free or subsidized parking drove an extra 3.1 miles to commute and 1.0 miles for non-work trips. Employees who were offered free or subsidized transit drove 3.2 miles less for commuting and 1.2 miles less for non-work trips. A complementary model controlling for built-environment variables reduced the magnitudes of the effects but showed the same direction for each.
“Spillover” effects reinforce VMT effects from transit and parking subsidies, By Eric Sundquist at SSTI, June 1st, 2020 In News, TDMTags: parking, TDM, transit, VMT
We know that employer-provided free parking tends to increase auto-commute trips and that employer-provided transit passes tend to reduce auto-commute trips.
Research is less clear about the effect on vehicle-miles traveled (VMT), however, in part because we don’t know whether or how such employment practices might affect non-work travel. For example, auto commuters might have more opportunity to drive to non-work destinations because they have cars available at work. And transit commuters might choose to live in higher-accessibility neighborhoods.
A new paper by Eun Jin Shin of Sungkyunkwan University, using travel survey data from the Seattle area, sheds new light on the VMT question.
Compared to the median VMT of 19.2 miles per day, employees who were offered free or subsidized parking drove an extra 3.1 miles to commute and 1.0 miles for non-work trips. Employees who were offered free or subsidized transit drove 3.2 miles less for commuting and 1.2 miles less for non-work trips. A complementary model controlling for built-environment variables reduced the magnitudes of the effects but showed the same direction for each.
The study was motivated in part by research on similar “spillover” effects of telecommuting, which tend to undercut the benefits in reduced auto travel for commuting. In the case of transit and parking subsidies, however, it appears that the spillover effects tend to reinforce the commuting VMT effects.
Eric Sundquist is Director of SSTI.
Teleworking’s hidden environmental costs
Posted on May 18th, 2020 in News, Outcomes, TDMTags: TDM, VMT
By Eric Sunquist
Because of the COVID-19 pandemic and subsequent shelter-in-place orders, more Americans are teleworking. This has drastically reduced VMT and air emissions.
Policymakers may be tempted to try to encourage teleworking post-COVID-19 in order to keep the traffic down and the air clean. But as we’ve reported before, telework is probably not a great strategy for emissions reduction, due to several rebound effects. Teleworkers tend to live farther from job centers, in lower-density environments, leading to longer, more auto-dependent commutes when they do go into the office, as well as higher levels of non-work VMT.
Two new papers on the topic tend to reinforce that caution.
A French research team employed British travel survey data and structural equation modeling to investigate the relationships between workplace locations and carbon emissions. They find that teleworking is associated with higher emissions:
The recent development of telework arrangements is directly related to residential location: as highlighted in the literature review section, the NTS database confirms that teleworkers tend to live further from central business districts, resulting in significant car dependency and longer commute distances. Some recent studies, such as Shabanpour et al.’s, (2018) have made a case for teleworking policies, showing through an activity-based model that they have the potential to reduce network congestion and vehicular emissions specifically during rush hours. Our results show that although planners and policymakers have hypothesized that the development of telework could potentially reduce travel demand, those forecasts remain largely unmet….
The model shows that, in the United Kingdom, individuals who telework seem to have a greater impact on CO2 emissions than individuals with a fixed work location. The environmental impact is directly related to total weekly kilometers traveled for both work and non-work trips. As previously noted, rebound effects cancel out the positive effects of teleworking or further increase GHG emissions because more kilometers are traveled.
In the other paper, British researchers survey the literature for findings on overall energy impacts of telecommuting. The survey finds that telecommuting is associated with energy use reduction from fewer commutes and less office-building energy use, as well as rebound effects including longer commutes from residential dispersion, greater non-work travel, and induced travel for non-workers due to the availability of an auto not used for commuting.
The majority of studies find a reduction in energy use from telecommuting. However, many of the studies are limited, e.g., focusing only on commuting and ignoring non-work travel, or have other methodological issues. The studies with the best methodology are much more mixed, with seven finding a net reduction in energy use, five finding an increase, and two others either neutral or unclear. (The survey did not include the newly published study summarized above.)
The authors conclude that “despite the positive evidence for energy savings that was found across the sample of studies, we should be cautious in drawing conclusions about the scale and consistency of energy savings from teleworking.”
Eric Sundquist is Director of SSTI.
