Road Safety Research, Policing and Education Conference, 2000, Brisbane, Queensland, Australia. Paper

A method was developed for estimating the overall reduction in casualty crashes on metropolitan Adelaide roads given a reduction in free travelling speeds. For example, it was found that a 5 km/h “free speed” reduction for all vehicles would be expected to lower the number of metropolitan Adelaide casualty crashes by more than 15 per cent. The method also allows the effects of speed changes on casualty crashes to be assessed independently for local, collector, undivided arterial or divided arterial roads.