Car Accident Newsroom

Cars Involved In Casualty Crashes Were Generally Traveling Faster Than Cars That Were Not Involved In A Crash

Cars involved in casualty crashes were generally travelling faster than cars that were not involved in a crash: 68 per cent of casualty crash involved cars were exceeding 60 km/h compared to 42 per cent of those not involved in a crash. The difference was even greater at higher speeds: 14 per cent of casualty crash involved cars were travelling faster than 80 km/h in a 60 km/h speed zone compared to less than 1 per cent of those not involved in a crash.

None of the travelling speeds below 60 km/h was shown to be associated with a risk of involvement in a casualty crash that was statistically significantly different from the risk at 60 km/h. Above 60 km/h there is an exponential increase in risk of involvement in a casualty crash with increasing travelling speed such that the risk approximately doubles with each 5 km/h increase in travelling speed.

By working back from the risk estimates we have concluded that nearly half (46 per cent) of these free travelling speed casualty crashes probably would have been avoided, or reduced to non-casualty crashes, if none of the case vehicles had been travelling above the speed limit. A more conservative estimate, based on calculation of stopping distances and impact speeds, indicates that 29 per cent of crashes would have been avoided altogether, with a reduction of 22 per cent in the impact energy of the remaining cases.

Using the second, more conservative, method we also estimate that a 10 km/h reduction in the travelling speeds of the crash involved cars in this study would probably have resulted in a reduction of at least 42 per cent in the number of crashes. A 5 km/h reduction showed much less effect but would still have resulted in a reduction of at least 15 per cent in the number of crashes.

Again using the conservative method, we estimate that an urban area speed limit of 50 km/h on all roads, with the present level of compliance, would be likely to result in a reduction of at least 33 per cent in the number of free travelling speed casualty crashes. However, a speed limit of 50 km/h in local streets, while having a significant effect on local street crashes, would be likely to have only a small effect on free travelling speed casualty crashes as a whole (a 6 per cent reduction) due mainly to the very small proportion (14 per cent) of these crashes which occurred on local streets.