Safety effects of restricting the speed limit from 90 to 70 km/h

Abstract

The Flemish government decided in 2001 to lower speed limits from 90 to 70 km/h at different regional roads. This study examines the effectiveness of this measure, through the application of a before-after study with a comparison group. A total of 61 road sections with a length of 116 km were included. At the majority of these road sections the speed limit was restricted in 2001 or 2002. The comparison group consisted of road sections with an unchanged speed limit of 90 km/h during the total research period. From this, 19 road sections were selected, with a total length of 53 km. Taking trend into account, the analyses show a 5 percent decrease in the crash rates after the speed restriction. This result is not significant, however upper bound is close to 1. Crashes with serious injuries and fatalities showed a decrease of 9%, also non-significant. Separate analyses were executed for crashes that occurred at intersection and at road sections. Those analyses showed a higher effectiveness of the speed restriction at road sections, both for injury crashes and more severe crashes. Also a higher effectiveness was found for the severe crashes compared to the injury crashes.