Pairing Speed Limit Reductions and Infrastructure to Lower Fatal and Serious (FSI) Crashes

While recent California legislative reforms grant jurisdictions greater flexibility to lower speed limits, evidence suggests that reductions in posted speed limits alone are insufficient to meaningfully reduce crash severity. This research brief examines how speed limit reductions, when paired with infrastructure design, enforcement strategies, and contextual land-use planning, can more effectively lower FSI outcomes. Aligned with the Safe System Approach, the countermeasure layers of roadway geometry, lighting, bicycle-specific infrastructure, and enforcement shape driver behavior and protect vulnerable road users. This approach provides a pathway for communities to advance vulnerable road user safety by reducing speeds through a holistic approach.