A brief analysis of road casualty reduction targets in Great Britain is given. This led to a study of un-survivable accidents involving cars to see if changes in numbers of fatalities could be explained. A flow diagram was developed using expert engineering judgement to represent the collision conditions believed to affect the survivability of a car accident. Co-operative Crash Injury Study data were used for the analysis. Belted vehicle occupants in frontal, side, rear and rollover impacts were analysed separately. Unbelted occupants were considered separately. The data were analysed using the Chi-squared automatic interaction detector technique. In frontal impacts, collision deformation classification (CDC) is identified as the primary variable and equivalent test speed (ETS), offside intrusion and occupant position are secondary variables distinguishing different rates of survival. Optimum ETS splits where survival rates are significantly different, were at 31 and 40 km/h. Offside intrusions particularly affected drivers because of their position in the vehicle. Side impacts involving a CDC exceeding 5 or a CDC of 4 and an ETS exceeding 27km/h, in rear impacts an ETS exceeding 56km/h and in rollover accidents a CDC exceeding 3 indicated high un-survivability. Males were over-represented in the results for high un-survivability. Changes in the numbers of killed and seriously injured casualties were not explained by changes in demographics.
Abstract