The relationship between free travelling speed and the risk of involvement in a casualty crash in a 60 km/h speed limit zone was quantified using a case control study design. The 151 case vehicles were passenger cars involved in crashes in the Adelaide metropolitan area which were investigated at the scene by the NHMRC Road Accident Research Unit and reconstructed using the latest computer aided crash reconstruction techniques. The 604 control vehicles were passenger cars matched to the cases by location, direction of travel, time of day, and day of week, and their speeds were measured with a laser speed meter. It was found that the risk of involvement in a casualty crash doubled with each 5 km/h increase in free travelling speed above 60 km/h. By comparing these risks with those associated with alcohol in a study also conducted by the NHMRC Road Accident Research Unit in Adelaide it was found that each 5 km/h increase in speed above 60 km/h increases the risk of a casualty crash by roughly the same amount as each increase in blood alcohol concentration of 0.05 g/l00 ml. (A)
Abstract