Lower speed limits may not slow drivers, a before-and-after study shows

Center for Transportation Studies, University of Minnesota
 By Megan Tsai
 March 12, 2024

A before-and-after study of speed changes in one Minnesota city shows that changing posted speed limits may not—at least initially—cause drivers to slow down. This new finding is important for Minnesota’s state and local transportation agencies as they continuously search for the most effective ways to reduce unsafe speeds and meet their Toward Zero Deaths safety goals.

“We know that physical modifications to a roadway such as speed humps, or strict police enforcement of speed limits, can reduce driving speeds, but the effectiveness of simply changing a speed limit is open to question,” says Gary Davis, a professor in the Department of Civil, Environmental, and Geo- Engineering.

Davis led a team that studied the effect of speed limit changes on vehicle speeds—absent other changes in the roadway environment—to help inform local speed limit policies and practices. The project was sponsored by the Minnesota Local Road Research Board (LRRB) and MnDOT.

View the full article: CTS.UMN.edu