Dividing Highways: Barrier Effects and Environmental Justice in California

Research Lead: Adam Millard-Ball

UC Campus(es): UCLA

Problem Statement: The racial legacy of freeways has come into stark focus in the past year. A recent Los Angeles Times article calls the region’s freeway system “one of the most noxious monuments to racism and segregation in the country.” A key feature of past freeways construction has been neighborhood severance. Freeways disrupt the neighborhood street grid, creating particular hardships for pedestrians who must take circuitous routes to access transit and to walk to stores, schools, and other destinations. The impacts of disconnected streets on walking and public health are well documented, but the environmental justice dimension of connectivity has remained unexplored, as has the link between street connectivity and local planning efforts. Reducing neighborhood severance is also a key goal in Caltrans’ 2017 bicycle and pedestrian plan, Towards an Active California. The plan commits the agency to identify and improve highway crossings and to prioritize improvements based on equity criteria.

Project Description: This project examined the barrier effects of freeways in California. It analyzed the association between freeways and three measures of nearby street connectivity: the composite Street Network Disconnectedness index (SNDi), circuity, and the distance between crossings – underpasses or bridges that enable people to cross the freeway. It also assessed the quality of a sample of these crossings for pedestrians and cyclists. The researchers found that that barrier effects are most pronounced in communities of color and that, even where crossings exist, they are unpleasant or even hazardous for pedestrians and cyclists because of high-speed traffic on on- and off-ramps, and because large volumes of traffic are funneled through a small number of crossings rather than being distributed over a wider network.

Status: Completed

Budget: $71,230