Baseline Research Program: Road Safety Evaluation of 40 Km/h Speed Zones In Victoria

This report describes a research study of the potential road safety benefits of 40 km/h speed limits on public roads. The study is based in Victoria, Australia, where 40 km/h speed limits are used in streets near schools, shopping strips, and also in neighbourhood areas. The study comprised two aims. First, to estimate the potential for change in crash and injury incidence given the introduction of 40 km/h speed zones in Victoria in areas currently zoned 50 km/h and 60 km/h. This was estimated by comparing the crash rate before and after introduction of the 40 km/h speed limit, to changes over the same time periods on roads where the speed zone remained the same (nominally a quasi-experimental design). The second aim was to describe attitudes and self-reported behaviours towards 40 km/h as a speed limit contrasted to other limits in a cross-section of adult drivers from Victoria. This was achieved through questions included in the TAC Road Safety Monitor on-line survey. The crash analysis estimated a reduction of 9.7% in all casualty crash types was associated with the introduction of 40 km/h speed limits on roads that previously had a 50 km/h or 60 km/h limit. Other estimates were determined for different crash populations. Of these, introduction of 40 km/h speed limits was associated with a 23.8% reduction in casualty crashes involving pedestrians. The crash analysis also found that there was no statistically significant difference in the change of nominally higher severity crashes relative to minor injury crashes. Higher severity crashes were indicated by a validated fatal or serious injury (hospitalisation) outcome, a Maximum Abbreviated Injury Score of 2+ or 3+, and a hospital stay greater than 1 day or 1 week. Opportunities to increase the number of locations at which a 40 km/h speed limit is applied are presented, along with the best estimate of the potential crash savings. The online survey of the driver community found a lower percentage of drivers reported having had intentionally exceeded a 40 km/h speed limit than other higher speed limits, and those that had exceeded this limit did so rarely. However, this was contradictory to limited speed data available for analysis which indicated rates of speeding in 40km/h zones were much higher than in 60km/h zones. Relationships between speeding behaviour and perceived risk of speed are also described. There were two key findings from this study. First, it indicated that there have been road safety benefits associated with introduction of 40 km/h speed limits, and there is scope for further crash savings. Second, the study found that road users may intentionally speed on roads with this limit less often than higher limits, although observed speeding behaviour shows rates of speeding are higher on 40 km/h roads. Research limitations and future directions are provided.