Monash University Accident Research Centre - Report #230 
Authors: Hoareau, E. and Newstead, S.V.
Full report in .pdf format [900KB]
This report presents the results of an evaluation of the default 50 km/h speed limits introduced in Western Australia on December 1, 2001. The study assessed the effects of the speed limit change in built-up areas on crash frequency, driver speed behaviour and community attitudes over the 24 month period following implementation of the program.
The crash effects of the initiative were measured using Poisson regression under a quasiexperimental design framework. Separate crash analyses were conducted for metropolitan Perth and regional Western Australia for various target groups and severity categories.
Results of the metropolitan analysis showed a 20% net reduction in all crashes, a 51% net reduction for all crashes involving pedestrians, and a 19% and 18% net reduction for all crashes involving young and older drivers, respectively. Although no statistically significant results were obtained for fatal or serious injury crashes in any of the analyses, a
statistically reliable net reduction of 21% was obtained for all casualty crashes. All major and minor property damage crashes were also reduced by 19% and 29%, respectively. Very few statistically significant results associated with the introduction of the program were obtained for the regional analyses. These included a net decrease of 16% for all
crashes, and a net reduction of 52% for crashes involving young drivers. Both of these results were valid for the first year of the program only.
An examination of speed monitoring surveys provided evidence that the intervention was associated with a positive effect on speeding behaviour, achieving statistically significant
reductions in excessive speeding in 50 km/h zones in both metropolitan Perth and regional Western Australia. Furthermore, an examination of community attitude surveys conducted
in the period prior to and post implementation, showed that support for the initiative had increased throughout this period. Both these findings are consistent with the crash analysis
Sponsoring organisations - Department of Premier and Cabinet of Western Australia