A Follow-up Evaluation of the 50km/h Default Urban Speed Limit in South Australia

On the 1 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.