The effect of vehicle roadworthiness on crash incidence and severity

Monash University Accident Research Centre - Report #164 [2000]

Authors: G. Rechnitzer, N. Haworth & N. Kowadlo

Full report in .pdf format [400KB]


The Road Safety Committee of the Victorian Parliament is conducting an Inquiry into Vehicle Roadworthiness, and the effectiveness of vehicle roadworthiness systems in reducing the incidence and severity of crashes. This study is in response to a request by the Victorian Automobile Chamber of Commerce (VACC) to assist in their submission in responding to Question 1 of the Parliamentary Committee’s Terms of Reference:

The extent to which vehicle roadworthiness is involved as a primary or contributing factor in crash causation”.

The work presented in this report covers both passenger cars and motorcycles (but not trucks), and comprises:

  • A literature reviewof Australian and international studies on the effects of vehicle defects, vehicle inspection systems, and ageing of cars.
  • An analysis of the Coroner’s Database (Victoria) for the period 1989-1998, to identify defective or unroadworthy vehicles and motorcycles that contributed to crashes.

Findings. There was significant variation in study findings regarding the role of vehicle defects in crash causation and the effectiveness of Periodic Motor Vehicle Inspections (PMVI) programs in reducing defects and crashes. Overall, it would appear that vehicle defects are a contributing factor in over 6% of crashes.

The effect of PMVI programs on accident rates as assessed by the studies varied significantly, from no effect to decreasing the accident rate by up to 16%. Few studies examined the effect of PMVI on the incidence of defects: a USA study found that it was associated with a 2.5% reduction; in Sweden, it was found that 7-8% of vehicles with serious defects were replaced after the introduction of PMVI. Some studies suggest that periodic roadworthiness tests could reduce the number of crashes caused by vehicle defects by about 50%.

Vehicle age was found to be an important factor. In Australia it was found that the odds of being involved in a fatal single vehicle crash were 2.5 times greater for a driver of a pre-1978 vehicle than a newer vehicle.

There are significant methodological and statistical difficulties and shortcomings in many of the studies, including the difficulty of identifying and detecting defects in crashed vehicles and their contribution to a crash. These problems would suggest an under-reporting of the contribution of defects to crashes.

From a safety viewpoint, it would appear axiomatic that vehicles need to be roadworthy and that this should be a prerequisite for their registration. What is really at issue is how this roadworthy condition can best be achieved and maintained.

Recommendations are made for further studies, including a comparison of defects found in the NSW and Victorian vehicle fleets.

Sponsoring organisation - Victorian Automobile Chamber of Commerce

See also PRSC Victoria's Vehicle Roadworthiness System