Accessibility moves out of the lab and into practice

By Eric Sundquist

Accessibility, long considered a more robust measure of transportation system success than simple mobility, is moving out of research and into practice, according to panelists on an SSTI webinar.

Accessibility measures the ease by which travelers can reach desired destinations, or “opportunities.” Often, but not always, it is measured in terms of time. As such, it combines both mobility and proximity of land uses, bringing together two directly connected public policy concerns that are often poorly integrated in decision-making.

While accessibility is not a new concept, data limitations have made it difficult to measure. Now it is becoming practice-ready, panelists said.

The webinar, broadcast Dec. 4, featured Andrew Owen of the University of Minnesota’s Accessibility Observatory, Richard Kuzmyak of Renaissance Planning Group, and Kate Sylvester of the Maryland DOT. Slides and a recording are available on the SSTI website.

Owen, who cited commentary in the conservative National Review and libertarian Reason Foundation about the benefit of accessibility measures, has been working with Minnesota DOT and now is developing a pooled fund study to mainstream accessibility measures across the country. Kuzmyak has applied accessibility measures in the Washington, D.C., area, including in a project with Sylvester’s Maryland DOT.

While both efforts aim to make use of accessibility for better transportation and land use decision-making, the approaches are somewhat different.

Owen’s group uses a cumulative opportunities count, generally using jobs as the critical opportunities. They estimate the number of opportunities that can be accessed by car and transit from neighborhoods around the nation within a set time, say 30 minutes.

Such an approach has the benefit of clarity, as the number of jobs is an “actual thing,” as Owen explained, and not a rating or score. On the other hand, in the interest of simplicity it does not address all the relevant data available, treating a job that is 30 minutes away as just as beneficial as one that is 30 seconds away, and assigning no benefit at all to one that is 30 minutes and 30 seconds away.

The Renaissance Group and Maryland DOT approach, on the other hand, uses a survey-based decay rate to assign benefit of opportunities by the time required to reach them, by mode (auto, transit, bike, and walk) and destination (work or non-work). In this respect it is similar to Walk Score, the well-known, commercially-available accessibility measure often used to market the walkability of housing in relation to dining, stores, and other opportunities. As has Walk Score’s creators, Renaissance has compared its measure to actual behavior and found it to be a useful predictor of actual behavior. Renaissance has applied the measure to planning questions in Northern Virginia in order to find places where bicycle-pedestrian facility improvements can convert trips from auto to non-auto.

Whether one or the other or both approaches proceed to become standard—or some other variant of accessibility does—the Minnesota and Renaissance/Maryland projects represent exciting new opportunities for planners and other decision-makers. SSTI, along with the Bipartisan Policy Center and the Eno Foundation, last year convened DOTs, MPOs, and others to discuss rulemaking for system performance measures under MAP-21. Participants generally agreed accessibility would be far superior to traditional mobility measures in judging the system based on benefits to users, but worried that data and methods were not yet available. The webinar panel showed clearly that data and methods are, in fact, practice-ready. Now it is up to practitioners to embrace accessibility and put it to good use in improving decision making.

Eric Sundquist is Managing Director of SSTI.