Creation and validation of a broadly applicable tool to measure the real population risk of speeding

Speeding is a significant contributor to the road toll. The risks associated with speeding at high and low levels are well understood, as are a range of speed management programs such as speed cameras to reduce speeding. Speed surveys are an effective tool to help quantify the population risk of speeding and to evaluate the impact of road safety interventions. They are especially useful because crashes are, statistically, a rare event and can be used to demonstrate the immediate impact of road safety interventions. The results of speed surveys are also usually available before the associated crash data has been collected and analysed. Their utility is diminished, however, through our use of crude, linear speed survey measurements such as mean, 85th percentile and percentage of drivers exceeding the speed limit. Recently D’Elia et al (2008), Doecke et al (2011), Gavin et al (2010) have combined known risk estimates with speed surveys to further our understanding of how the population level of risk of speeding can be described and evaluated through the use of speed surveys. This paper documents the development of a tool which translates speeding identified in speed surveys into a risk measure. The tool is designed to be used with annual speed surveys and speed surveys used to evaluate the impact of road safety interventions such as enforcement programs. The tool has been validated using NSW annual speed surveys against the road toll and the number of speed related fatal crashes.