Fatigue in Truck Accidents

Monash University Accident Research Centre - Report #3 - 1989

Authors: N. Haworth, C. Heffernan & E. Horne

Full report in .pdf format [720KB]

Abstract:

Based on Coroners' verdicts, fatigue of car or truck drivers was a contributing factor in 9.1% of fatal accidents involving trucks. Based on the presence of factors such as extended driving hours, falling asleep at the wheel, comments about tiredness, driving right of centre and night-time driving, the authors estimated fatigue contributed to 19.9% of the accidents. There were approximately equal numbers of fatigued car drivers and truck drivers.

An analysis of casualty and fatal truck accidents by time of day (adjusted for exposure) showed that accident risks were highest during the night on all five Victorian highways studied. Driver fatigue is one of the possible factors underlying this pattern of elevated risk.

The report section described in-vehicle fatigue countermeasures. The distinction between fatigue monitors and alerting devices was made and it was recommended that eye closure and head nodding monitors and an alerting device be tested in the next stage of this project.

Executive Summary

This report is one of several to be produced as part of a study of driver fatigue in truck accidents. It presents two estimates of the involvement of fatigue in Victorian truck accidents and a review of in-vehicle fatigue countermeasures to select devices for testing in the second stage of the project. The study was commissioned by the Victorian Road Freight Transport Industry Council and funded by the Road Construction Authority of Victoria in May, 1988.

Coroners' reports were analysed to

  • provide an estimate of the degree of involvement of fatigue in fatal Victorian accidents involving trucks which occurred in the period 1984-86 and to
  • collect preliminary data on the incidence of mechanical defects in the sample of fatal accidents involving trucks.

The Coroner concluded that fatigue was a contributing factor in 9.1 % of the sample of fatal accidents involving trucks. This figure was made up of car-driver fatigue in 5.4% of the accidents, articulated vehicle-driver fatigue in 3.2% of the accidents and fatigue on the part of rigid truck drivers in 0.5% of the accidents. (The differences between car and truck drivers are not statistically significant.)

An alternative estimate of the contribution of fatigue was calculated by classifying as fatigue-related those accidents which involved several of the factors: extended driving hours, evidence of falling asleep at the wheel, comments about tiredness, driving right of centre in the absence of elevated BAC and night-time driving. This resulted in a judgement that fatigue was involved in 19.9% of the sample of fatal accidents involving trucks. This figure was made up of fatigue on the part of car drivers in 12.4% of the accidents, fatigue of drivers of articulated vehicles in 6.5% and fatigue of drivers of rigid trucks in 1.1 % of the accidents. The percentage of car drivers fatigued is statistically significantly greater than the percentage of articulated vehicle drivers.

Both estimates from Coroners' verdicts and the authors' judgement may be unreliable because of selective reporting in the Coroners' records lowering the estimates of fatigue in accident-involved truck drivers. Truck drivers more often survive the accident to provide witness information, which may bias the available evidence.

Truck mechanical defects were considered by the Coroner to have been a probable cause in five crashes and a possible cause in another four crashes. Tyre defects were the most common type of mechanical defect for both articulated and rigid vehicles. For articulated vehicles, five of nineteen owner-driven trucks had a defect (26.3%) and three of 58 trucks driven by another person were defective (5. 1 %). There were few defects in rigid trucks. While these results are in accord with the concern about maintenance neglect by owner-drivers, the results are based on such a small number of defects that such an interpretation may be premature.

An estimate of the involvement of fatigue in all accidents involving trucks as an exposure-corrected function of time of day was calculated from dat7a obtained from the Road Traffic Authority's accident data base and traffic counts made by the Road Construction Authority. The analysis showed that accident risks were highest during the night on all five Victorian highways studied. Driver fatigue is one of the possible factors underlying this pattern of elevated risk.

The third section describes in-vehicle fatigue countermeasures and recommends devices for testing in the second stage of the project. Devices to monitor levels of driver fatigue based on psychophysiological measures of fatigue (eye closure and head nodding monitors) and measures of vehicle control behaviour (monitors of steering pattern and tachographs) are discussed. Fatigue countermeasures which function by maintaining driver alertness include reaction time devices (e.g., Roadguard) and driver strategies (auditory input, control of cabin temperature and alerting 'games').

It is recommended that the Onguard eye closure monitor, a head nodding monitor and the Roadguard alerting device undergo laboratory testing in the next stage of this project. The criteria which will be applied in testing are reliability, criterion level and degree of intrusiveness.

A separate volume has been produced which presents information about the onset of fatigue to enable the development of an educational program for heavy vehicle drivers to assist in the prevention of fatigue-related accidents.

Sponsors: Road Construction Authority and the Victorian Road Freight Transport Industry Council