In harm's way : a study of Northern Territory linked crash records

Background This study was commissioned by the NT Road Safety Task Force to identify factors underpinning the NT’s excessive level of road trauma and quantify their impact on the injury outcomes of Indigenous and non-Indigenous road traffic casualties. It was conducted using a linked dataset of NT public hospital crash-related admission records from the HMD matched to NT Police crash records from the VADB during a nine-year period 1999–2007. Aim This study aimed to provide answers to three research questions:  How useful is a linked dataset as a tool for identifying the relationship between contributing factors and injury outcomes among road traffic casualties?  What is the impact of ethnicity on the relationship between contributing factors and injury outcomes among road traffic casualties?  Which factors have most influence on fatal and ‘high threat to life’ injury outcomes, among Indigenous and non-Indigenous casualties? Literature review The literature review identified that the NT consistently has the worst road toll of all Australian jurisdictions and Organization for Economic Cooperation and Development (OECD) member countries. There were marked differences between the types of road users and the severity of injury among Indigenous and non-Indigenous casualties. Certain factors associated with crash occurrence and injury outcome were more prominent among crashes involving Indigenous casualties. Methods Using LinkageWiz linkage software, a study dataset comprising 2,818 linked hospital and police crash records was constructed, using probabilistic matching methods. Descriptive analyses described the crash-related injury burden among people injured or killed on NT roads. Analytical analyses examined the relationship between factors and injury outcome among Indigenous and non Indigenous casualties and the relationship between factors and crash outcome, according to Indigenous status of the person at fault. Multivariable logistic regression modelling using manual backward stepwise selection methods identified factors with most influence on severe injury outcome among vehicle occupants. Results The linkage rate was 54% and comparable with other linkage studies. The study dataset was useful for quantifying the proportion of ambulance casualties who require admission to hospital and the burden of life threatening injuries among NT casualties. Indigenous casualties were twice as likely to die from a road crash as non-Indigenous casualties, but just as likely to survive. Vehicle passengers and pedestrians predominated among Indigenous casualties, whereas among non-Indigenous casualties, drivers were the most commonly injured road user type followed by passengers and motorcyclists. Intoxication was shown to be far more problematic if an Indigenous person was responsible for a crash, particularly if the person was a pedestrian. Multivariable modelling identified four factors with the most influence on severity of injury among vehicle occupants. These included being involved in an alcohol-related crash, being unrestrained and ejected from a vehicle and travelling in a defective vehicle. Speed and fatigue failed to show significance when examined in the presence of other factors. Discussion The linked dataset proved to be a highly valuable and efficient mechanism for large scale assessment of the relationship between causal factors and injury outcomes among road traffic casualties. Establishing the linked dataset was challenging and there remain substantial limitations in the attribution of causal factors using the available data (see Limitations section). However, the combination of available information through the linkage of the police and hospital datasets enabled a rigorous evaluation of the contribution by previously noted factors plus identification of several under-appreciated factors and a better estimate as to the extent of over representation of severe road trauma among certain population groups and road user types. Key contributing/causal factors included alcohol and negligence, misuse of seat-belts and defective vehicles. Overseas visitors and Indigenous pedestrians were over-represented. Finally, it demonstrated the lower than expected impact of certain key factors including speed and fatigue. Conclusion This study identified the prevalence of certain behavioural patterns is still high among road traffic casualties in the NT. Furthermore, the large number of pedestrian deaths represents a crisis for Indigenous people in the NT, who frequently experience the heartbreaking loss of family members due to this preventable death. The link between pedestrian carnage and social deprivation is strong, and in the absence of measures to break this seemingly inextricable association, pedestrians will continue to account for over 40% of Indigenous fatalities.