The research team set out to answer these key research questions:
- How did the road diet impact traffic volume and speed along the road diet segment and surrounding streets?
- How did the impacts vary by time of day?
- What strategies can be used to improve road diet evaluations?
According to Dr. Hilary Nixon, “the road diet impacts vary considerably by location and time of day. The most aggregated measures, that is average all-day impacts for a specific street type, obscure important findings at specific location, as well as variations in impacts by time of day.” Within the road diet zone, traffic volumes and the number of speeders both fell with peak periods showing greater percentage declines than all-day counts. Outside the road diet zone, traffic volumes fell slightly or remained flat, although the number of speeders rose, particularly along major streets. Fortunately, most of the neighborhood streets saw less pronounced changes and the number of new speeders was low.
Several policy recommendations were put forth by the research team to improve future road diet evaluations. First, without careful planning, it is easy to spend considerable time and money collecting road diet evaluation data that ultimately does not allow evaluators to assess impacts with any certainty or nuance. Second, it is important to analyze and present impacts for each data collection location, as well as by street types, by time of day, as well as by all-day metrics, and to look at both actual change in counts as well as percentage change. Designing graphics that emphasize the changes between pre- and post-periods is also important.
The report is available for free download from http://transweb.sjsu.edu/
ABOUT THE AUTHORS
Hilary Nixon, PhD and Asha Weinstein Agrawal, PhD are professors of urban & regional planning at San José State University. Cameron Simons is a housing market analyst at Trulia.
ABOUT THE MINETA TRANSPORTATION INSTITUTE
At the Mineta Transportation Institute (MTI) at San Jose State University (SJSU) our mission is to increase mobility for all by improving the safety, efficiency, accessibility, and convenience of our nation's’ transportation system through research, education, workforce development and technology transfer. We help create a connected world.
MTI was founded in 1991 and is funded through the US Departments of Transportation and Homeland Security, the California Department of Transportation, and public and private grants. MTI is affiliated with SJSU’s Lucas College and Graduate School of Business.
Hilary Nixon, Ph.D., MTI Director of Research and Technology Transfer
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