Vehicle Crashworthiness and Aggressivity Ratings and Crashworthiness by Year of Vehicle Manufacture

Victoria and NSW Crashes During 1987-98, Queensland Crashes During 1991-98

Monash University Accident Research Centre - Report #171 - 2000

Authors: Newstead, S.V., Cameron, M.H., Le, C.M

Full report in .pdf format [940KB]

Abstract:

Crashworthiness ratings measure the relative safety of vehicles in preventing severe injury to their own drivers in crashes whilst aggressivity ratings measure the serious injury risk vehicles pose to drivers of other vehicles with which they collide. Crashworthiness and aggressivity ratings for 1982-98 model vehicles were developed based on data on crashes in Victoria and New South Wales during 1987-98 and in Queensland during 1991-98. Crashworthiness and aggressivity were measured by a combination of injury severity (of injured drivers) and injury risk (of drivers involved in crashes). The ratings were adjusted for the driver sex and age, the speed limit at the crash location, the number of vehicles involved, the state in which the crash occurred and the year in which the crash occurred. These factors were strongly related to injury risk and/or severity for both aggressivity and crashworthiness. Both ratings estimate, with the appropriate focus, the risk of a driver being killed or admitted to hospital when involved in a tow-away crash, to a degree of accuracy represented by the confidence limits of the rating in each case.

The crashworthiness estimates and their associated confidence limits were sufficiently sensitive that they were able to identify 58 models of passenger cars, four-wheel drive vehicles, passenger vans and light commercial vehicles that have superior or inferior crashworthiness characteristics compared with the average vehicle. Aggressivity rating estimates and their associated confidence limits were sufficiently sensitive that they were able to identify 23 models of passenger cars, four-wheel drive vehicles, passenger vans and light commercial vehicles that have superior or inferior aggressivity characteristics compared with the average vehicle. Also investigated was the relationship between vehicle crashworthiness and the year of manufacture of Australian vehicles manufactured from 1964 to 1998. Cars, station wagons and taxis manufactured during the years 1964 to 1998 were considered.

The results of this report are based on a number of assumptions and warrant a number of qualifications that should be noted.

Executive Summary

This report describes the development of further updated crashworthiness ratings and aggressivity ratings for 1982-98 model vehicles. Crashworthiness ratings measure the relative safety of vehicles in preventing severe injury to their own drivers in crashes whilst aggressivity ratings measure the serious injury risk vehicles pose to drivers of other vehicles with which they collide. Both measures are estimated from data on real crashes. The update is based on crash data from Victoria and New South Wales during 1987-98 and from Queensland during 1991-98. The rating of vehicle crashworthiness through analysis of real crash data, as carried out here, and through crash tests carried out by consumer groups such as the Australian New Car Assessment Program has encouraged manufacturers to improve vehicle safety.

Both crashworthiness and aggressivity were measured by a combination of injury severity (of injured drivers) and injury risk (of drivers involved in crashes). Crashworthiness injury severity was based on 151,354 drivers injured in crashes in the three States during 1987-98. Crashworthiness injury risk was based on 648,829 drivers involved in crashes in New South Wales and Queensland where a vehicle was towed away. Aggressivity injury risk was based on 418,212 drivers involved in crashes between two vehicles in New South Wales and Queensland where a vehicle was towed away. Aggressivity injury severity was based on 106,057 drivers injured in two-car crashes in the three States during 1987-98.

The crashworthiness and aggressivity ratings were adjusted for the driver sex and age, the speed limit at the crash location, the year in which the crash occurred and the state in which the crash occurred. Crashworthiness ratings were also adjusted for the number of vehicles involved in the crash. These factors were found to be strongly associated with injury risk and injury severity. Adjustments were made with the aim of measuring the effects of vehicle factors alone, uncontaminated by other factors available in the data that affected crash severity and injury susceptibility.

The crashworthiness rating scores estimate the risk of a driver of the focus vehicle being killed or admitted to hospital when involved in a tow-away crash, to a degree of accuracy represented by the confidence limits of the rating in each case. Statistically reliable crashworthiness ratings were calculated for 167 individual vehicle models. The estimates and their associated confidence limits were sufficiently sensitive that they were able to identify 58 models of passenger cars, four-wheel drive vehicles, passenger vans and light commercial vehicles that have superior or inferior crashworthiness characteristics compared with the average vehicle.

Aggressivity ratings were calculated for 96 models of Australian passenger vehicles (passenger cars, four-wheel drive vehicles, passenger vans and light commercial vehicles) manufactured between the years 1982-98. Aggressivity rating scores estimate the risk of a driver of a vehicle impacting with the focus vehicle being killed or admitted to hospital when involved in a tow-away crash. The degree of accuracy of the aggressivity ratings is represented by the confidence limits of the rating in each case. The estimates and their associated confidence limits were sufficiently sensitive that they were able to identify 23 models of passenger cars, four-wheel drive vehicles, passenger vans and light commercial vehicles that have superior or inferior aggressivity characteristics compared with the average vehicle. Estimated vehicle aggressivity towards drivers of other vehicles was found to have a proportional relationship with vehicle mass. It was also found to have little or no relationship with ratings of vehicle crashworthiness, demonstrating the independence of the two complementary measures.

It is concluded that the additional crash data has enabled the crashworthiness and aggressivity ratings to be obtained for a larger range of car models than was previously possible. The expanded data set has been able to produce more up-to-date and reliable estimates of the crashworthiness of individual car models than those published previously. However, the results and conclusions are based on a number of assumptions and warrant a number of qualifications that should be noted.

A final stage of the project investigated the relationship between vehicle crashworthiness and the year of manufacture of vehicles for the years of manufacture 1964 to 1998. This study updated an earlier one that studied vehicles manufactured in the years 1964 to 1997.

The crashworthiness of passenger vehicles (cars, station wagons and taxis), measured by the risk of the driver being killed or admitted to hospital as the result of involvement in a tow-away crash, has been estimated for the years of manufacture 1964 to 1998. Similar to the original study, this study showed improvements in crashworthiness over the period of study, with the greatest gains over the years 1970 to 1979 during which a number of new Australian Design Rules aimed at occupant protection took effect. Gains in crashworthiness have also been observed over the years 1989 to 1998.

Sponsoring Organisations: Road Traffic Authority of NSW , Royal Automobile Club of Victoria Ltd., NRMA Ltd., VicRoads, Royal Automobile Club of Western Australia Ltd. and by a grant from the Australian Transport Safety Bureau.