Trends in crashworthiness of the New Zealand vehicle fleet by year of manufacture: 1964 to 2009. Supplement to report 304 Vehicle safety ratings estimated from police reported crash data: 2011 update.

Crashworthiness is an estimate of the occupant protection provided by a vehicle, namely the risk of a driver of a vehicle being killed or admitted to hospital when involved in a crash. The relationship was investigated between vehicle crashworthiness and both the year of manufacture and the year of first registration in New Zealand of New Zealand light passenger vehicles manufactured from 1964 to 2009 and crashing during 1991 to 2009. The latter analysis was aimed at assessing crashworthiness trends in the fleet of used imported vehicles in New Zealand whilst the former examined trends in the fleet as a whole. Crashworthiness was measured by a combination of injury severity (of injured drivers) and injury risk (of drivers involved in crashes). The ratings were adjusted for the sex and age of the driver, the speed limit at the crash location, the number of vehicles involved in the crash and the year in which the crash occurred. The crashworthiness rating estimates the risk of the driver being killed or admitted to hospital when involved in a crash, to a degree of accuracy represented by the confidence limits of the rating in each case. Analysis of trends by year of vehicle manufacture showed statistically significant improvement in the crashworthiness of New Zealand light passenger vehicles over the years of manufacture studied. Most of the measured improvement occurred over the years of manufacture from 1983 to 2008. Over this period, the risk of death or serious injury to drivers reduced by over 71% for the fleet as a whole. During this period vehicle safety in New Zealand was affected by several competing effects: a general increase in both active and passive safety features in vehicles; increasing proportions of used imported vehicles entering the New Zealand fleet; and increases in the regulation of vehicle safety standards by the New Zealand Government. Estimates of crashworthiness trends in the used import vehicle fleet by year of first registration in New Zealand from 1986 to 2009 showed improved crashworthiness of the fleet over these years. There is some suggestion that improvements in crashworthiness of vehicles manufactured in the most recent years is much greater for vehicles sold new in NZ compared to those imported second hand. This offers some cause for concern and should be monitored closely. The results of this report are based on a number of assumptions and warrant a number of qualifications that should be noted. (Author/publisher)