Fleet modelling

The profile of the age and types of vehicles in the fleet has a fundamental influence on road safety. This is because there have been considerable advances in the safety of vehicles over the past 40 years and there is significant variation in the safety of different market groups and models vehicles within each age group. The VSRG research program has modelled the safety impacts of various fleet composition changes in response to changes in consumer purchasing patterns driven by changing preferences and policy. These are demonstrated in the following publications.

4WD crash involvement risk

  • Keall, M.D. & Newstead, S. INDUCED EXPOSURE ESTIMATES OF ROLLOVER RISK FOR DIFFERENT TYPES OF PASSENGER VEHICLES Traffic Injury Prevention, Volume 10, Issue 1, 2009, pp. 30 – 36.


    This study aimed to model rollover risk of New Zealand and Australian passenger vehicles to identify which driver and vehicle factors were associated with the highest risk of rollover. A further objective was to test the feasibility and reliability of the quasi-induced risk estimation approach for studying rollover risk. Higher rollover risk was found for those vehicle types with a relatively high center of gravity compared to the width of the wheel track, namely sport utility vehicles (SUVs) and people movers. The quasi-induced exposure method produced very consistent estimates of rollover risk despite large differences in the crash recording systems and crash type definitions used in the four jurisdictions studied.

  • Keall, M.D. & Newstead, S. SELECTION OF COMPARISON CRASH TYPES FOR QUASI-INDUCED EXPOSURE RISK ESTIMATION Traffic Injury Prevention, Volume 10, Issue 1, 2009, pp. 23 – 29.


    The objective of this study was to find a comparison crash type that best represented exposure on the road and to identify situations where the induced exposure risk estimates were likely to be biased. This research identified some important features of crash occurrence useful for making choices of comparison crash types when controlling for exposure.

  • Keall, M.D. & Newstead, S. ARE SUVS DANGEROUS VEHICLES? Accident Analysis and Prevention. 40, 3 (2008), 954–963.


    The objective of the study was to evaluate the effect on road safety of sports utility vehicles (SUVs) compared to other passenger vehicle types. Controlling for distance driven, vehicle and owner characteristics, SUVs were found to be relatively safe vehicles in terms of injury crash involvement and in terms of the injury rate of their own occupants or other road users into which they crashed.

Retrospective and prospective vehicle safety effects

  • D'Elia, A.D. & Newstead, S.V. 2015, CONTRIBUTION OF VEHICLE SAFETY IMPROVEMENTS AND INFRASTRUCTURE INVESTMENT ON REDUCING ROAD TRAUMA IN VICTORIA AND PROJECTED FUTURE BENEFITS, Proceedings of the 2015 Australasian Road Safety Conference, 14-16 October 2015, Australasian College of Road Safety, Gold Coast, Australia, pp. 1-12. See the Australian College of Road Safety publications database.


    The aim of this work was to estimate the impact of each road safety program area on road trauma as represented by measured improvements in the light vehicle fleet and major investment in safer infrastructure through the TAC funded Safer Road Infrastructure Program (SRIP), and to project their future benefits. Time series models were constructed over the period 2006 to 2014 with separate models developed for fatalities and serious injuries. These models were then used to produce forecasts of future trends in deaths and serious injuries. It was evident that each program area has been very successful in achieving significant savings in death and serious injury.

  • Budd, L. and Newstead, S. PRIORITIES FOR FUTURE VEHICLE SAFETY IMPROVEMENTS IN THE WESTERN AUSTRALIAN LIGHT VEHICLE FLEET Proceedings, Australasian Road Safety Research, Policing and Education Conference, 12-14 November 2014, Melbourne, Australia. See the Australian College of Road Safety publications database.


    This project aimed to model the potential road trauma reductions that could be achieved in Western Australia through safer vehicle choices, particularly for Government and Corporate fleets. A specific aim was to identify safety technologies or vehicle purchasing strategies that could lead to the greatest and most cost-effective road trauma reductions. Universal fitment of forward collision warning and autonomous emergency braking systems operating at all speeds was the scenario estimated to provide the greatest reductions in injuries and associated societal costs.

  • Newstead, S.V.THE CONFLICT BETWEEN FUEL PRICES, ENVIRONMENTAL CONCERNS AND VEHICLE SECONDARY SAFETY: INSIGHTS FROM THE USED CAR SAFETY RATINGS Proceedings 2009 Australasian Road Safety Research Policing Education Conference, November, Adelaide, Australia.

  • Keall, M. & Newstead, S. (2005) PROJECTING EFFECTS OF IMPROVEMENTS IN PASSIVE SAFETY OF THE NEW ZEALAND LIGHT VEHICLE FLEET TO 2010, Proceedings Australasian Road Safety Research Policing Education Conference, 14-16 November, Wellington, New Zealand, Submitted Papers CD-ROM, 11p.


    This paper describes a methodology for projecting changes in casualty rates associated with passive safety features, including the effects of two potential interventions: restrictions on the importation of cars into New Zealand and restriction of government fleet vehicles to those with superior crashworthiness. Compared to the quite large social cost reduction of about 22% expected to occur largely due to improvements in the crashworthiness of the fleet over time, these additional interventions were predicted to yield fairly modest savings.

  • Oxley, P., Newstead, S. & Cameron, M. (2003) ESTIMATION OF THE SAFETY BENEFITS OF A VEHICLE REPLACEMENT PROGRAM IN VICTORIA, Proceedings 2003 Road Safety Research, Policing and Education Conference, 24-26 September, Sydney, Roads and Traffic Authority, NSW, CD-ROM.


    This study aimed to estimate the benefits of a program of replacing older passenger vehicles in Victoria. Explicitly, the question posed is what programs would be suitable in Victoria to bring about a reduction in the vehicle fleet age, with the overall aim being to bring about a more crashworthy fleet. Based on current trends, such as population rates, new vehicle sales and market group trends, a scrappage function by age of vehicle was estimated to project the vehicle fleet to 2012.

  • Keall, M., Newstead, S. & Jones, S. Projecting effects of improvements in passive safety of the New Zealand light vehicle fleet to 2010, Traffic Injury Prevention, 2006:8(3), 275 – 280.


    The objective of this paper is to describe a methodology for projecting changes in casualty rates associated with passive safety features and to apply this methodology to produce an updated prediction to the one made in the year 2000 - that there would be a 15.5 percent reduction in social cost associated with improvements in crashworthiness.  A large social cost reduction of about 22 percent for 2010 compared to the year 2000 was predicted due to the expected huge impact of improvements in passive vehicle features on road trauma in New Zealand.

  • Budd, L., Keall, M. & Newstead, S. RETROSPECTIVE AND PROSPECTIVE CHANGES IN SECONDARY SAFETY OF THE AUSTRALIAN AND NEW ZEALAND VEHICLE FLEETS AND THE POTENTIAL INFLUENCE OF NEW VEHICLE SAFETY TECHNOLOGIES. Monash University Accident Research Centre, Report No. 329, October 2016.


    This project estimated the impact of improvements in secondary safety of the Australian and New Zealand vehicle fleets on fatalities over the years 2000 to 2010 and projected the future benefits expected to 2020 under two scenarios: business as usual (where secondary safety improvements continue following current trends) and stalled safety (where secondary safety ceases to improve in vehicles manufactured in the future). Over the years 2000 to 2010, the average crashworthiness of the Australian light vehicle fleet has improved by 27% representing a saving of around 2,000 deaths over the time period. Improvement in the crashworthiness of the New Zealand fleet has also been significant with an improvement in average crashworthiness of 18% representing a saving of 313 lives over the years 2000-2010.

  • Keall, M. D. & Newstead, S.V. THE EFFECT OF MARKET GROUP MIX ON CRASH RISK IN THE AUSTRALASIAN LIGHT VEHICLE FLEET. Monash University Accident Research Centre, Report No. 295, 2010.


    The objective of this study was to examine potential crash risk and injury effects of wholesale changes in market preference within the light passenger vehicle fleets of New Zealand, NSW and Victoria. The study found important differences between the New Zealand light passenger vehicle fleet and the fleets in NSW and Victoria in vehicle age and crash patterns. For example, the New Zealand fleet was on average much older than the NSW and Victorian fleets – probably influenced by the widespread importation of used vehicles from Japan – and, a much larger proportion of crashes occurred on higher speed limit roads compared to the two Australian states.

Trends in secondary safety

  • Newstead, S. & Watson, L. (2005) TRENDS IN CRASHWORTHINESS OF THE NEW ZEALAND VEHICLE FLEET, Proceedings Australasian Road Safety Research Policing Education Conference, 14-16 November, Wellington, New Zealand, Submitted Papers CD-ROM, 13p. See the Australian College of Road Safety publications database.


    This paper summarises the work in MUARC Report 238. The aim of this project was to investigate the relationship between vehicle crashworthiness and vehicle year of manufacture for the New Zealand passenger vehicle fleet as a whole. A key outcome of the study was that there was a statistically significant improvement of 50% in the crashworthiness of New Zealand light passenger vehicles over the study period (1991-2002).

  • Newstead, S. & Watson, L. TRENDS IN CRASHWORTHINESS OF THE NEW ZEALAND VEHICLE FLEET BY YEAR OF MANUFACTURE: 1964 TO 2002. Monash University Accident Research Centre, Report No. 238, April 2005.


    The aim of this project was to investigate the relationship between vehicle crashworthiness and vehicle year of manufacture for the New Zealand passenger vehicle fleet as a whole.  A key outcome of the study was that there was a statistically significant improvement of 50% in the crashworthiness of New Zealand light passenger vehicles over the study period (1991-2002).

  • Newstead, S., Watson, L. & Cameron, M. TRENDS IN AGGRESIVITY OF THE AUSTRALIAN LIGHT VEHICLE FLEET BY YEAR OF MANUFACTURE AND MARKET GROUP: 1964-2000. Monash University Accident Research Centre, Report No. 214, March 2004.


    The relationship between vehicle aggressivity and the year of manufacture of Australian passenger and light commercial vehicles manufactured from 1964 to 2000 was 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 2000. When considering the vehicle fleet as a whole, no long-term trend to improving or worsening aggressivity by year of manufacture was identified.

  • Newstead, S., Watson, L., Delaney, A. & Cameron, M. CRASHWORTHINES AND AGGRESIVITY OF THE AUSTRALIAN LIGHT VEHICLE FLEET BY MAJOR RASH TYPE. Monash University Accident Research Centre, Report No. 227, June 2004.


    This report examines relative vehicle crashworthiness and aggressivity of the Australian light passenger vehicle fleet in the four major crash types in which they are involved. These are single vehicle crashes, crashes with unprotected road users such as pedestrians and bicyclists, crashes with heavy vehicles and crashes with other light passenger vehicles. Results of the research have been able to identify the vehicle market groups that have relatively good and bad secondary safety performance in each crash type considered.

Other Fleet Modelling publications

  • Budd, L., Newstead, S., & Watson, L. VSRG RESEARCH PROGRAM: AN ANALYSIS OF HEAVY VEHICLE SAFETY PERFORMANCE IN AUSTRALIA, Report No. 354, 2021.


    Heavy vehicle travel in Australasia is predicted to continue to grow faster than for other vehicle types. Without further intervention, such increases will likely increase the number of heavy vehicle drivers involved and injured in road crashes. This project addresses the knowledge deficit by quantifying the heavy vehicle safety problem associated with various heavy vehicle types using Australian and New Zealand Police reported crash data of 2006 to 2017.

  • Keall, M.D. & Newstead, S.V. PASSENGER VEHICLE SAFETY IN AUSTRALASIA FOR DIFFERENT DRIVER GROUPS Accident Analysis and Prevention 43,3 (2011), 684–689.


    Vehicle fleets in developed countries have benefitted from improved technology and regulation leading to safer vehicles. Nevertheless, for various reasons the public do not necessarily choose particular makes and models of cars according to their safety performance. This study aimed to identify areas for potential crashworthiness improvement in the Australasian fleets by studying the distribution of these fleets according to vehicle age and estimated crashworthiness.

  • Keall, M. D. & Newstead, S.V. CHARACTERISTICS OF VEHICLES DRIVEN BY DIFFERENT DRIVER DEMOGRAPHICS – HOW CAN SAFER VEHICLE CHOICES BE ENCOURAGED? Monash University Accident Research Centre, Report No. 301, 2010.


    This study examined the profile of vehicles driven by different driver groups in different jurisdictions of Australasia to investigate the secondary safety of the vehicles driven. Specifically, data from the years 2001-2005 from NSW, Victoria, Queensland, Western Australia, South Australia and New Zealand were included in the analysis of the following factors: vehicle age, crash type, vehicle market group, vehicle crashworthiness, driver age, and driver sex. A key finding of the study was the relationship between vehicle age and driver age; within each jurisdiction the crash fleet of younger drivers was oldest, the fleet for drivers aged 26-59 the newest, and the older drivers’ fleet in-between.

  • Delaney, A. & Newstead S. THE INFLUENCE OF TRENDS IN HEAVY VEHICLE TRAVEL ON ROAD TRAUMA IN THE LIGHT VEHICLE FLEET. Monash University Accident Research Centre, Report No. 259, 2007.


    This study examines the effect of anticipated growth in heavy vehicle travel on road trauma in the light passenger vehicle fleet. Exposure data was sourced from BTRE and the ABS in conjunction with the NSW Police reported crash database and was used to develop a model to project relevant future trends in road trauma to reflect three key elements of the road trauma chain: exposure, crash risk and injury outcome given crash involvement.

  • Delaney, A. & Newstead, S. (2006) THE INFLUENCE OF TRENDS IN HEAVY VEHICLE TRAVEL ON ROAD TRAUMA IN THE LIGHT VEHICLE FLEET. Proceedings Australasian Road Safety Research Policing Education Conference, 25-27 October, Gold Coast, Queensland, Submitted Papers CD-ROM. See the Australian College of Road Safety publications database.


    This paper examines the effect of anticipated growth in heavy vehicle travel on the light passenger vehicle fleet by measuring changes in road trauma levels as measured by the number of light vehicle driver fatalities and serious injuries resulting from collisions with heavy vehicles. The results demonstrate the sensitivity of heavy vehicle related road trauma to crash risk and highlight the importance of continuing to reduce heavy vehicle crash rates to offset projected growth in heavy vehicle travel and deliver reductions in heavy vehicle related road trauma.

  • Keall, M. & Newstead, S. SUITABILITY OF NZ WOF DATA FOR VEHICLE CRASH RISK ESTIMATION, Report to Land Transport New Zealand, 2006.
  • Keall, M., Newstead, S. & Watson, L. FOUR-WHEEL DRIVE VEHICLE CRASH INVOLVEMENT PATTERNS Report PP 06/05, Royal Automobile Club of Victoria, 2006.