Examining the Relationship between Community Design and Crash Incidence

This study seeks to understand how urban form—specifically land use and street network configurations— may influence the incidence of traffic-related crashes injuries and deaths. It begins with an historic overview of the safety concepts that directed community design practice during the 20th century and details how these design concepts transformed themselves into contemporary community design practice. It details the development of a database of crash incidence and urban form at the block group level for the City of San Antonio, the first such database of its kind. Data acquired from this database are then modeled using negative binomial regression models to determine how urban form may be associated with the incidence of traffic-related crashes, injuries, and deaths at the block group level. It finds that the presence of arterial thoroughfares, strip commercial uses, and big box stores are significantly related with increased crash risk, while the presence of more traditional, pedestrian-scaled retail configurations are associated with a reduction in crash incidence. The population density of a block group was similarly associated with a reduction in crash incidence. Intersections had a mixed effect, reducing fatal crashes, but at least in the case of 4-leg intersections, also increasing the incidence of total and injurious crashes. Based on these findings, this study discusses the implications for design practice and outlines three strategies for enhancing traffic safety through community design.