Basing Transportation Policies on Accessibility

How do we assess if an urban planning effort improves accessibility to essential destinations? This is the question at the heart of Xiang Yan's article, "Toward Accessibility-based Planning: Addressing the Myth of Travel Cost Savings," in the Journal of the American Planning Association (Vol. 87, No. 3).

Transit Accessibility Affects Household Location Choice

In the article, Yan argues that while many planners and planning scholars agree that accessibility is a major policy goal, they have primarily only assessed if efforts improve accessibility by whether or not they accrue travel cost savings (TCS), such as savings on households' commuting costs and reductions in vehicle miles traveled (VMT). However, several common efforts thought to encourage accessibility — such as transit-oriented development and location-efficient neighborhoods — have been shown in studies to not have major TCS-related benefits. Therefore, TCS-focused criteria may determine that they do not improve accessibility.

Yan, however, argues that planners need to broaden the accessibility criteria we are using to evaluate these efforts. Drawing on Walter Hansen's definition of accessibility as "the potential for people to interact with spatially distributed opportunities," Yan proposes a second criterion that he terms "destination utility gains," referring to the personal satisfaction that one receives from being able to interact with and choose between desirable destinations. In other words, an effort's impact on accessibility must be assessed not only on how it reduces people's overall travel time and distance but also on how it allows them to travel to more of the places where they might want to go. Both of these factors will influence someone's transportation experience and thus will influence their experience of where they live.

Table 4: Residential location choice models in Southeast Michigan region.

Broadening Support for Accessibility Planning

To test this impact of destination utility gains on where households choose to live (the outcome variable), Yan uses a discrete choice modeling approach for two regions of the U.S. to examine access to transit — Puget Sound, Washington, and Southeast Michigan. The author finds that transit accessibility was positive and significant in each of the models used, including those models that control for TCS-related variables (see Table 4). This suggests that households generally prefer to live in zones with higher transit accessibility and that this preference is not solely influenced by their desire to reduce travel costs, but also by the potential for destination utility gains, as Yan suggests.

Yan adds that this finding can help planners garner wider support for accessibility-based planning efforts by showing the public the destination utility gains they will make available, such as "activity participation, gains from destination diversity, and knowledge spillover from enhanced personal interactions." Therefore, the piece will be especially useful for planners looking to make the argument for a particular initiative's broader accessibility benefits beyond TCS.

Top image: Oregon Department of Transportation flickr.com (CC by 2.0)