An assessment of the factors associated with fatal outcomes for motor vehicle occupants in South Australia (1981-2020)

Abstract

Vehicle occupants account for a large majority of the fatalities resulting from motor vehicle crashes. Despite the overall downward trend in occupant fatalities in Australia in recent decades, the number of occupant fatalities has begun to plateau, suggesting that there is a subset of crashes that remain lethal. The long-term objective of the National Road Safety Strategy (2021-2030) is to achieve zero road fatalities by 2050 and, therefore, more in-depth research into fatal crashes is needed. Current road crash databases are often engineeringfocused and lack data that relate to injuries, in turn limiting the extent to which factors that contribute to fatal injury can be investigated. The aim of this research was to highlight the benefits of combining data from a police-reported crash database with fatal injury information obtained from coronial autopsy reports. A database of 2800 occupant fatalities combining variables from the Traffic Accident Reporting System (TARS) and coronial autopsy reports was established. Several publications are presented within this thesis that sample from the larger combined dataset. One publication compares the trends in methamphetamine detection and blood alcohol concentration above 0.05g/100mL in driver fatalities, finding an upward trend in methamphetamine detection and a significant downward trend in BAC detection between 2008 and 2018. The presence of significant cardiac disease was also assessed in a sample of fatally injured drivers, finding no significant difference in prevalence between the drivers and a control sample of fatally injured passengers. The presence of seat belt markings was investigated in two publications. Increasing body mass index (BMI) was found to be associated with the presence of seat belt marking as was bilateral pelvic fracture; however, no other injuries were predictive of seat belt markings. Secondly, season of year, as a proxy measure for the amount of clothing worn, changed the incidence of seat belt markings. During winter months the incidence of seat belt markings significantly decreased, suggesting that clothing imposition may mask cutaneous trauma. Increasing age was found to be significantly associated with the number and pattern of rib fractures. Finally, a case series reporting limb amputations in vehicle-related fatalities found that higher impact speed was associated with limb amputation. Several other research questions explored the interactions between various occupant, crash and injury factors to further expand our understanding of these factors and how they contribute to patterns of fatal injury. Two common themes emerged, the first being that increasing age is strongly associated with injuries such as rib fractures and cervical and thoracic spinal fractures but, unexpectedly, was not associated with other injuries such as atlanto-occipital fracture. The other was BMI, with high BMI being protective against some abdominal injuries while conversely increasing other injuries. There were also three review publications, including an overview of classification of cause of death, vehicle-related suicides and lethal airbag injuries. The results found in this thesis also highlight the complexities of gathering data retrospectively. The amalgamation of various crash-related databases can provide greater understanding of contributing factors, with the aim of reducing and eliminating motor vehicle fatalities.