TRENDS IN CRASHWORTHINESS OF THE NEW ZEALAND VEHICLE FLEET Stuart Newstead and Linda Watson Monash University Accident Research Centre ABSTRACT Crashworthiness ratings measure the relative safety of vehicles in preventing death or serious injury to their drivers in crashes. This study has successfully estimated trends in the crashworthiness of the light passenger vehicle fleet in New Zealand by both year of manufacture and year of first registration in New Zealand. Years of vehicle manufacture from 1964 to 2002 have been considered through analysis of data on police reported crashes involving injury in New Zealand over the period 1991 to 2002. Estimates have been obtained for the fleet as a whole as well as broken down by vehicles sold new in New Zealand and vehicles imported second-hand. There was statistically significant improvement of 50% in the crashworthiness of New Zealand light passenger vehicles over the study period. The majority of the measured improvement occurred from 1983 to 2002, a period in which New Zealand vehicle safety was affected by several competing factors including engineering improvement, increasing used vehicle imports and increased Government regulation. Level of absolute crashworthiness and trends on a year of manufacture basis were similar for used imports to those for vehicles sold new in New Zealand. Estimated crashworthiness trends of used import vehicles by year of first registration in New Zealand showed statistically significant improvements from 1978 to 1998. Absolute levels of crashworthiness and improvements by year of first registration paralleled those seen in the analysis by year of manufacture but occurred some 6 years later, a lag equivalent to the average age of the used imported vehicles over the study period. Implications of the used import program on overall vehicle safety in New Zealand are discussed. BACKGROUND AND AIMS Background Crashworthiness ratings assess the relative performance of different vehicle models in preventing injury to their occupants in the event of a crash. A system of rating vehicle crashworthiness by examining injury outcomes to drivers in real crashes has been developed by the Monash University Accident Research Centre (MUARC, Newstead et al, 2004). The rating is a measure of the risk of death or serious injury to a driver of that vehicle when it is involved in a crash. This risk is estimated from large numbers of records of injury to drivers involved in crashes reported to police. A principal focus of the MUARC crashworthiness ratings study has been to track historical improvements in the average crashworthiness of the Australian vehicle fleet by year of manufacture since 1964. The study has showed that the crashworthiness of passenger vehicles in Australia has improved over the years of manufacture 1964 to 2002 (Newstead et al, 2004). Particularly rapid improvement was observed over the years from about 1970 to 1979 in response to the implementation of a number of Australian Design Rules (ADRs) for motor vehicle safety which previous research had shown to be effective in providing occupant protection.