Characteristics of rollover crashes

This paper analyses data from an in-depth study of 236 rural crashes, including 64 in which a vehicle
rolled over. These analyses are supplemented by some data from police reports on crashes, to examine the characteristics of rollover crashes in South Australia. The risk of a crash being a single vehicle rollover increases markedly at higher travelling speeds and eighty per cent of them were initiated by the vehicle running at least partially onto the left unsealed shoulder. Road and traffic related countermeasures such as audio-tactile edge lining and sealed shoulders are noted, as is the potential to reduce the risk of a crash being a single vehicle rollover by reducing rural speed limits. The paper concludes with a brief discussion of the design of vehicles in relation to rollover crashes, including the
benefits of electronic stability control.
A series of 236 rural road crashes to which an ambulance was called within 100 km of Adelaide was
investigated by the Road Accident Research Unit (now the Centre for Automotive Safety Research,
CASR) between March 1998 and February 2000. Unit personnel attempted, usually successfully, to
reach the scene of the crash before the vehicles were moved. Vehicle positions and damage were
recorded and the site was mapped and photographed. Participants and witnesses were interviewed in
most cases, initially at the scene in some cases and later in follow up interviews. In some fatal cases,where the vehicle positions had been marked by the Police Major Crash Investigation Unit, the CASR investigating team examined the crash scene within 24 hours. This had the effect of increasing the proportion of fatal crashes in the sample.
The sample of crashes investigated is not fully representative of all crashes occurring in the study area because the investigating teams were on call more frequently during daylight hours from Monday to Friday than on weekends. Similarly, night time crashes were under represented, apart from Thursday and Friday nights. However, characteristics associated with single vehicle rollover crashes can reasonably be compared with corresponding characteristics associated with other types of crash in this sample.
Some comparisons are made with data on all reported crashes in South Australia from the Traffic Accident Reporting System (TARS). These comparisons are influenced by the inclusion of crashes in the metropolitan area of Adelaide in the State-wide TARS data and by differences due to the study area including most of the hill country in the State.