Vehicle Safety Ratings Estimated from Police Reported Crash Data: 2009 Update
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VEHICLE SAFETY RATINGS ESTIMATED FROM POLICE REPORTED CRASH DATA: 2009 UPDATE AUSTRALIAN AND NEW ZEALAND CRASHES DURING 1987-2007 by Stuart Newstead Linda Watson & Max Cameron Report No. 287 August 2009 Project Sponsored By ii MONASH UNIVERSITY ACCIDENT RESEARCH CENTRE MONASH UNIVERSITY ACCIDENT RESEARCH CENTRE REPORT DOCUMENTATION PAGE Report No. Report Date ISBN ISSN Pages 287 August 2009 0 7326 2357 X 1835-4815 (On-Line) 82 + Appendices Title and sub-title: VEHICLE SAFETY RATINGS ESTIMATED FROM POLICE REPORTED CRASH DATA: 2009 UPDATE AUSTRALIAN AND NEW ZEALAND CRASHES DURING 1987-2007 Author(s) Type of Report & Period Covered Newstead, S.V., Watson, L.M and Cameron, M.H. Summary Report, 1982-2007 Sponsoring Organisations - This project was funded as contract research by the following organisations: Road Traffic Authority of NSW, Royal Automobile Club of Victoria Ltd, NRMA Motoring and Services, VicRoads, Royal Automobile Club of Western Australia Ltd, Transport Accident Commission, New Zealand Transport Agency, the New Zealand Automobile Association, Queensland Department of Transport and Main Roads, Royal Automobile Club of Queensland, Royal Automobile Association of South Australia and by grants from the Australian Government Department of Transport, Infrastructure, Regional Development and Local Govenrment and the Road Safety Council of Western Australia Abstract: This study describes the calculation of updated vehicle safety ratings that measure the relative safety of vehicles in preventing severe injury to people involved in crashes. Three different aspects of secondary safety are examined: crashworthiness which focuses on drivers of the rated vehicle, aggressivity which focuses on drivers of other vehicles and unprotected road users such as pedestrians, cyclists and motorcyclists colliding with the rated vehicle and total secondary safety which examines the combined crashworthiness and aggressivity performance of the rated vehicle. Updated ratings for 1982-2007 model vehicles were estimated based on data on crashes in Victoria and New South Wales during 1987-2007, in Queensland, Western Australia and New Zealand during 1991-2007 and in South Australia during 1995-2007. Each rating is measured as a combination of injury severity (the risk of death or serious injury given an injury was sustained) and injury risk (the risk of injury given crash involvement). The ratings were adjusted for the sex and age of the person whose injury outcome was being measured, speed limit at the crash location, number of vehicles, crash configuration and type or road user involved where relevant, the jurisdiction in which the crash occurred and the year in which the crash occurred. These factors were strongly related to injury risk and/or severity. The ratings estimate the risk of 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. A new method of presenting the ratings for consumer information is introduced. The new rating presentation classifies vehicles according to where their rating lies in relation to a best performance benchmark. Crashworthiness estimates and their associated confidence limits were obtained for 427 vehicle models classified into 10 market groups with 203 models of vehicles identified as having ratings of adequate statistical precision to be compared to the crashworthiness benchmark rating of 1.60%. Aggressivity rating estimates and their associated confidence limits were obtained for 397 vehicle models with 154 having ratings of sufficient statistical precision to be compared to the aggressivity benchmark rating of 1.93%. The total secondary safety index estimates and their associated confidence limits were obtained for 484 vehicle models classified into 10 market groups with 239 being of sufficient statistical precision to be compared to the total safety index benchmark index of 1.91%. The relationship between vehicle crashworthiness and the year of manufacture of Australian passenger and light commercial vehicles manufactured from 1964 to 2007 was also investigated. Trends were examined by year of manufacture both for the fleet as a whole and by market group for vehicles manufactured from 1982 to 2007. The results of this report are based on a number of assumptions and warrant a number of qualifications that should be noted. Key Words: (IRRD except when marked*) Injury, Vehicle Occupant, Collision, Passenger Car Unit, Passive Safety System, Statistics Disclaimer: This Report is produced for the purposes of providing information concerning the safety of vehicles involved in crashes. It is based upon information provided to the Monash University Accident Research Centre by VicRoads, the Transport Accident Commission, the New South Wales Roads and Traffic Authority, NRMA Ltd, Queensland Transport, the Western Australian Department of Main Roads, South Australian Department of Transport, Energy and Infrastructure and Land Transport New Zealand. Any republication of the findings of the Report whether by way of summary or reproduction of the tables or otherwise is prohibited unless prior written consent is obtained from the Monash University Accident Research Centre and any conditions attached to that consent are satisfied. A brochure based on this report is available from the sponsoring organisations and may be freely quoted. Reproduction of this page is authorised Monash University Accident Research Centre Building 70, Monash University Victoria 3800, Australia. Telephone: +61 3 9905 4371, Fax: +61 3 9905 4363 VEHICLE SAFETY RATINGS: 2009 UPDATE iii EXECUTIVE SUMMARY This report describes the development of further updated vehicle safety ratings for 1982- 2007 model vehicles. The ratings produced cover vehicle crashworthiness, aggressivity and total secondary safety. 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 other road users with which they collide. The aggressivity rating measure is based on collisions between the vehicle being rated and both other vehicles and unprotected road users including pedestrians, bicyclists and motorcyclists. The total secondary safety index measure integrates into one measure the combined crashworthiness and aggressivity performance of a vehicle in a way most representative of the crash population involving the vehicle fleet being rated. It considers relative injury outcomes in a mix of crashes involving light passenger vehicles including single and multi vehicle crashes, crashes with heavy vehicle and crashes involving unprotected road users. It was first developed in Newstead et al (2007a) to represent the total secondary safety performance of the vehicle across the full range of collision partners and crash types. All three measures of vehicle secondary safety performance are estimated from data on real crashes reported to police. The update is based on crash data from Victoria and New South Wales during 1987-2007, from Queensland, Western Australia and New Zealand during 1991-2007 and from South Australia during 1995-2007. 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 Australasian New Car Assessment Program is aimed at informing consumers about relative vehicle safety performances as well as encouraging manufacturers to improve vehicle safety. A new method of presenting the ratings for consumer information is introduced. The new rating presentation classifies vehicles according to where their rating lies in relation to a best performance benchmark. Crashworthiness ratings 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 348,618 drivers injured in crashes in Victoria during 1987-2007, in New South Wales during 1987-1998, in South Australia during 1995-2007 and in Queensland, Western Australia and New Zealand during 1991-2007. Crashworthiness injury risk was based on 1,831,574 drivers involved in crashes in New South Wales during 1987-2007, in South Australia during 1995-2007 and Western Australia and Queensland during 1991-2007 where a vehicle was towed away or someone was injured. The crashworthiness ratings were adjusted for the driver sex and age, the speed limit at the crash location, the year in which the crash occurred, the jurisdiction in which the crash occurred and 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 non-vehicle related factors available in the data that affected crash severity and injury susceptibility. The crashworthiness ratings 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. Crashworthiness ratings and their iv MONASH UNIVERSITY ACCIDENT RESEARCH CENTRE associated confidence limits were calculated for 427 individual vehicle models manufactured between the years 1982-2007. The estimates and their associated confidence limits were sufficiently sensitive that they were able to identify 203 models of passenger cars, four