The contribution of driver fatigue to casualty and fatal crashes in South Australia

Abstract

Determining whether fatigue (referring to a person falling asleep or experiencing deficits in functioning due to being tired, drowsy, or sleepy) is involved in a motor vehicle crash is difficult. Consequently, there is high variability in estimates of the contribution of fatigue to crashes. This study explored the contribution of driver fatigue to casualty and fatal crashes in South Australia, as well as the role that fatigue played in the crashes, the risk factors that led to the fatigue and the countermeasures that could have prevented the crashes. Data from two sources were examined: in-depth at-the-scene investigations of casualty crashes by the Centre for Automotive Safety Research (2014 to 2019) and Coroner reports on fatal crashes (2014 to 2015). Fatigue-related crashes were identified through evaluation of various forms of evidence (e.g., from crash participant/witness interviews, events preceding the crash). Fatigue contributed to 4.3% of casualty crashes and 11.5% of fatal crashes. Most fatigue crashes occurred during daylight hours (72.4%), on high-speed roads (86.2%), and at midblock locations (89.7%), and most (82.8%) involved the driver falling asleep, leading to the vehicle departing its lane, and either rolling over or colliding with a roadside object or oncoming vehicles. The most common risk factors for fatigue were long distance driving (41.4% of crashes), no/reduced/broken sleep (27.6% of crashes), illicit drug use (17.2% of crashes), and abnormal work/sleep routines (17.2% of crashes). The countermeasures that could have prevented the most fatigue crashes were lane keep assist (could have prevented 79.3% of crashes), lane departure warnings (65.6%), drowsiness detection/warnings (55.2%), audio tactile centre lines (41.4%), and autonomous emergency braking (34.5%). Vehicle technologies, therefore, comprised four of the five most common countermeasures. This study was the first, of which the authors are aware, to estimate the contribution of driver fatigue to crashes within South Australia.