Impact of Speed Limit Changes on Urban Streets

Abstract

In 2019 the Minnesota Legislature amended that state's statutes to allow cities to set speed limits on city-owned streets. In February 2021 we surveyed 33 cities within the Twin Cities metro area and identified the city of St. Louis Park as planning to implement a city-wide change in speed limits, with a default speed limit of 20 mph but with selected roads being signed for limits ranging from 25 mph to 35 mph. Speed data was collected using road tube traffic recorders in the summer of 2021, 2-4 months before the speed limit change, and in the summer of 2022, 6-8 months after the change. There was considerable variability regarding what was seen at individual locations, with before/after differences in mean speed ranging from a decrease of 7 mph to an increase of 2.4 mph. On average, mean speeds were slightly lower (1-2 mph) in the after period, both on streets where the speed limit was lowered and on streets where the limit was unchanged. This pattern, modest reductions in mean speeds following a reduction in speed limit, with possible spillover, was consistent with what has been seen in other cities in North America and Great Britain.