Institute of Transportation Studies at UC Berkeley

Traffic calming is increasingly used by cities as a strategy to reduce speeding, improve safety, and support walking and biking on neighborhood streets. While many studies and evaluations focus on whether traffic calming is effective on the street where it is implemented, far less attention has been paid to what happens beyond the treated street. In practice, traffic calming interventions can influence driver behavior, traffic volumes, and perceptions of safety on nearby streets, producing spillover effects that can be positive, negative, or unevenly distributed. Understanding these spillover effects is especially important as cities like Oakland scale up neighborhood traffic calming programs as part of broader Vision Zero and Safe System strategies.