A follow up evaluation of the 50km/h default urban speed limit in South Australia

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. An initial evaluation one year after the change showed that vehicle speeds and crashes had reduced on local roads with the 50 km/h limit and also on arterial roads that were signposted at 60 km/h. This paper reports the results of a follow up evaluation three years after the DUSL was introduced. Vehicles speeds were measured at the same 52 randomly chosen sites across the State. On-road speeds just before the default limit was introduced were compared with speeds measured one and three years later. Crash data was analysed by examining the crash history of all roads with a 50 km/h or 60 km/h speed limit, three years before and after the new DUSL was introduced. The study found that, on average, mean speeds had fallen by approximately 3.8 km/h on streets where the speed limit was reduced and by 2.1 km/h on arterial roads where 60 km/h speed limit signs were erected. There was a 23% reduction in casualty crashes on 50 km/h roads and a corresponding 16% reduction on 60 km/h arterial roads.