Abstract

In the United States, local governments typically evaluate the transportation impacts of new development based on the expected effects of the development on nearby traffic flows. These flows are most often measured in terms of “level-of-service,” or LOS, from “A” (free flow) to “F” (forced flow). If a traffic impact analysis (TIA) finds that the LOS on streets and intersections near the proposed development will degrade below a certain threshold, the project developer may be required to undertake mitigation efforts, including funding nearby transportation system improvements to lessen the projected traffic delays occasioned by the new development and/or reduce the scale of the proposal — or they may risk the project not being approved at all. LOS mitigation frequently ignores travel via modes — such as walking, biking, scooters, or public transit — other than motor vehicles. This emphasis on nearby traffic effects and motor vehicle mobility can discourage development in already built-up areas and, in doing so, ignore both the project’s regional effects on travel and traffic and the economic, social, and environmental benefits that arise from agglomerations of activities.In response, a growing number of researchers and practitioners have argued that an accessibility-focused approach would be a more conceptually complete and practical way to assess the transportation effects of new developments. Accessibility analyses consider the ease by which various destinations can be accessed by foot, bike, and public transit, as well as by car, and how proposed new developments might change this. As the number of accessibility adherents in planning research and practice has grown, there has been significant progress in the development of access evaluation measures and tools. For this research, we (1) developed a conceptual framework for accessibility analysis (Figure 1), (2) used this framework to assess the promise and pitfalls of 54 measures and tools developed to evaluate access, and (3) conducted interviews with five practitioners around the U.S. to learn about early efforts to incorporate access measurement into planning practice.