• July 24th, 2023

This study examined the effects of posted speed limit changes on traffic safety by conducting before-and-after assessments using crash and speed data from multiple sites.

Despite numerous studies reporting the negative impacts of increased speeds on traffic safety, many states have raised their posted speed limits. In response, the AAA Foundation for Traffic Safety (AAA Foundation) initiated a multiphase study in 2018 to investigate the effects of posted speed limit changes. The first phase entailed gathering feedback from traffic engineers on how posted speed limits are set and what factors they consider in changing posted speed limits. The second phase involved a collaborative effort with the Insurance Institute for Highway Safety and Humanetics Innovative Solutions to examine how vehicle crashworthiness and occupant protection degrade as impact speed increases. The final phase comprised before-and-after assessments of crash and speed profile data collected from sites where posted speed limits were raised or lowered, and examination of any differences between sites.

Read the full study here.