Lower VMT of TOD the result of density more than rail

By Robbie Webber

A study published in the Journal of the American Planning Association argues that the rail transit frequently used to define transit-oriented development is not the most important factor in reducing vehicle miles traveled and car ownership. Overall density and the availability of parking were shown to be the most important variables in predicting reduced driving.

In reviewing this study, authored by David Chatman of the University of California-Berkeley, Atlantic Cities concludes that this is actually an encouraging result, because land near high-capacity transit is limited. Encouraging the other characteristics of TOD and limiting parking can reduce driving without the expense of developing new rail lines.

Transit-oriented development often is assumed to work best when focused around rail stations. Because rail is a significant capital investment, developers of residential and commercial properties, potential residents, and business tenants feel confident that the transit service will be continue to be available. The cost of rail projects and the laying of rails means the transit lines won’t be abandoned or the routes changed.

However, the expense of rail lines also can mean that development of TOD is stalled while transit is planned and funded. But the study authors found that reduced driving can be achieved without rail. Neighborhoods with access to frequent and multiple local bus or bus rapid transit lines also show fewer trips and lower car ownership than those without convenient rail service—as long as the neighborhoods were also dense and featured a mix of uses, small and rental housing, jobs, and proximity to other daily amenities. The proximity of grocery stores to housing was noted as a factor in limiting driving as well. Holding these other factors constant, rail access became much less important.

Most intriguing, the authors point to the availability of on- and off-street parking as the strongest indicators of reduced driving and car ownership. Chatman’s study found that households located in neighborhoods with scarce parking cut their car trips to the store by one-quarter, regardless of proximity to a rail station. Yet, in a literature review, he found there are few studies investigating this phenomenon, citing work by Rachel Weinberger of the University of Pennsylvania as an exception.

Chatman’s research studied ten communities in New Jersey, with proximity to the CBD in New York also cited as a strong factor in limiting driving, The MinnPost speculated about whether the research could shape zoning and parking regulations in Minneapolis. Recent research from the Humphrey School of Public Affairs at the University of Minnesota interviewed employers regarding their interest in and barriers to the development of TOD. While access to transit was highly valued, employers found that zoning and parking minimums often made developing TOD difficult. They also felt torn between accommodating the car commutes of current employees and appealing to new, younger potential employees who value a more transit-friendly workplace.

The Humphrey School study recommended changes to zoning, economic development, construction policies, and parking requirements to facilitate TOD in the Twin Cities and transition to a less car-dependent workforce.

Robbie Webber is a Senior Associate at SSTI.