Evaluation of the 50km/h default urban speed limit in South Australia

Abstract

On the 1st March 2003 the Default Urban Speed Limit (DUSL) in South Australia was lowered from 60 km/h to 50 km/h. Since this date, all urban roads have a speed limit of 50 km/h unless otherwise signed. This paper reports the results of an evaluation of the effectiveness of the reduced DUSL and is based on speed surveys and crash data analysis. Vehicles speeds were measured at 52 randomly chosen sites across the State. Crash data was analysed by examining the crash history of all roads with a 50 km/h or 60 km/h speed limit, a year before and after the new DUSL was introduced. The study found that, on average, mean speeds have fallen by approximately 2.2 km/h on streets where the speed limit was reduced and by 0.7 km/h on arterial roads where 60 km/h speed limit signs were erected. There was a 19.8% reduction in casualty crashes on 50 km/h roads and a corresponding 4.6% reduction on 60 km/h arterial roads when compared with the previous year.