Rollover Propensity

ACRS Policy Position

The rollover propensity should be assessed and clearly indicated for all passenger vehicles driven in Australia (sedan, wagon, 4WD and MPVs). That Electronic Stability Control systems be installed into all new vehicles.

Objective

• To improve the intrinsic safety of passenger vehicles and thus reduce the consequences of driver error and road hazards.
• To support and encourage the reduction of inherent rollover propensity particularly in vehicles with higher centre of gravity such as 4WD and MPVs.
• To promote correct understanding of the risks and benefits of purchasing a vehicle with a reduced rollover propensity.

Discussion

Rollover crashes account for approximately 22% of passenger cars in fatal crashes in Australia^[i] and yet only represent approximately 10% of fatal road crashes. Rechnitzer et al.[ii] reported on an Australian based study of rollover, using 1988 Federal Office of Road Safety (FORS) Fatality File data that rollovers; "constitute 19% of occupant fatalities in Australia." The problem of rollover is magnified further when vehicles are operated in a non-urban environment. Rechnitzer et al. reported that; "rollover crashes are a common cause of occupant injury especially on non-urban roads.  They constitute to 44% of occupant fatalities in rural Western Australia and 54% in rural Northern Territory"

Henderson et al. ^[iii],[iv] reported on an Australian based for FORS, using 1988, 1990 and 1992 FORS Fatality File data that; "rollover crashes, especially in the country, are usually very destructive events.  About 15% of passenger cars in fatal crashes in Australia have overturned.  Between about 13% and 16% of all passenger-car occupants killed in Australia died primary as a result of injuries received in a rollover."

Vehicle rollovers remain one of the major crash types yet to be dealt with in terms of effective vehicle design  countermeasures and performance standards.  This is despite the progress in understanding how rollovers occur, increased knowledge of vehicle handling technology, the development of occupant protection measures, sophisticated crash modelling software, and greatly improved injury and crash testing measurement laboratory systems. Although crash prevention is the preferred countermeasure for all crash types, this is particularly true for rollovers.  Whereas for most crashes serious or fatal injury outcomes are typically related to crash severity, this is less true for rollovers where fatal or serious injuries can still occur in low energy rollover events due to partial occupant ejection.

It is imperative that Australia adopts a test procedure for rollover propensity. A methodology for testing and ranking rollover propensity has been proposed by Richardson et al [v]^,[vi] and is being implemented in Australia by fleet owners who are at particular risk of rollover crashes. This methodology needs to be urgently adopted for all vehicles driven in Australia.

The importance of rollover prevention has been recognized in the USA, in particular, where some 10,000 fatalities per annum occur due to rollovers.  Recent measures to reduce rollover risk have included the introduction of a five-star rating vehicle rating system based on rollover propensity using a vehicle Stability Factor approach.  Such a system is aimed at simultaneously informing Consumers as well as encouraging improved vehicle design by manufacturers (particularly for SUV type vehicles).

More recently the Insurance Institute for Highway Safety have found Electronic Stability Control (ESC) reduced fatal single-vehicle crash risk by about 56 percent and reduced the risk of all single-vehicle crashes (fatal and nonfatal) by 41 percent.[vii] Such stunning reductions in regards to ESC fitted vehicles are also being noted in Europe. Australia needs to follow the lead set by the USA and Europe.

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