The purpose of this study was to develop injury-based costs for Australia by body region and injury severity level of the Abbreviated Injury Scale (AIS). The AIS is a threat-to-life scale that classifies injuries by body region on a scale of minor, moderate, serious, severe and critical. Most other studies that have investigated the costs of road trauma have used the injured person or the crash as the costing unit rather than the injury. This study reports costs in Australian dollars for the year 2000.
The injury cost estimates produced in the study include (i) the direct resource costs of treating road injuries and (ii) the estimated costs associated with loss of functioning from sustaining an injury and its longer-term consequences. Included in the latter category of costs is loss of quality of life resulting from road injury. Two analytical approaches were adopted in calculating loss of quality of life: the Compensation approach used compensation payments made by a motor vehicle personal injury insurer as a proxy for loss of quality of life, and the Willingness to Pay approach attributed a portion of the value of statistical life to loss of quality of life based on the relative utility loss of the injury.
A Road Injury Cost Database was constructed that included approximately 93 800 cases of road crash casualties who had claimed compensation from a motor vehicle personal injury insurer in Australia. Costs were allocated to each case in the Road Injury Cost Database for the following range of cost components: health care resources, non-health care resources, productivity losses and loss of quality of life. Data sources for these cost components included compensation payment records of the motor vehicle personal injury insurer, national hospital cost data by Diagnostic Related Group, official statistics produced by the Australian Bureau of Statistics, road crash cost estimates produced by the Bureau of Transport Economics, and expert opinion provided by a panel of health care professionals. The cost of fatalities was factored into the cost estimates by taking a weighted average of the probability of a non-fatal injury outcome multiplied by the cost of a non-fatal outcome plus the probability of a fatal injury outcome multiplied by the cost of a fatal injury outcome for each injury severity level of the AIS.
Two stages were involved in producing the injury-based costs from the person-based costs in the Road Injury Cost Database. First, the person-based costs of cases with multiple injuries were allocated to their specific injuries based on the proportional average costs of these injuries for single injury cases. Second, injury-based unit cost estimates were calculated by adding together the costs of injury to each body region and severity level for all single injury and multiple injury cases, and then dividing this sum by the corresponding number of all injuries to each body region and injury severity level. Altogether the 93 800 cases in the Road Injury Cost Database comprised 37 200 single injury and 56 600 multiple injury cases. The total number of injuries to all cases was 191 700.
The average cost of a road injury was estimated as A$40 100 based on the Compensation approach and A$57 100 using the Willingness to Pay approach. The exchange rate in June 2000 was A$1 = US$0.5964. The results showed a wide variation in costs across body regions and severity levels. These cost differences are discussed below for the Compensation approach.
Overall, the most costly injuries were those to the head, spine and lower extremities with average costs per injury of A$113 700, A$57 000 and A$56 400 respectively. The least costly injuries were external injuries (A$15 600) and neck injuries ($18 200).
Costs increased with the level of injury severity from $21 500 for a minor injury to $974 900 for a critical injury. The average cost of an injury increased approximately 2.5 times as injury severity increased across each severity level from minor through to critical. Within severity levels, the variability in costs across body region was considerably greater for the more serious injuries than the less serious injuries. For example, the average costs of a minor injury ranged from $13 700 for an injury to the thorax to $27 400 for a spinal injury, while for a critical injury the average costs ranged from $322 800 for an injury to the thorax to $1.4 million for a spinal injury.
The average costs per injury of $40 100 can be compared with the equivalent average person-based costs of a road crash of A$82 000. Expressing unit cost estimates in relation to injury rather than based on persons or crashes is useful in evaluating the effectiveness of interventions that aim to reduce the injury severity level of a specific injury. Some secondary prevention measures seeking to prevent injury or reduce the severity of injury through, for example, the implementation of safety aids or devices, fall into this category.
An original aspect of this study was its inclusion of the cost of injuries to fatalities in the unit cost estimates. Including the cost of fatalities increased the average costs per injury from $36 700 to $40 100 based on the Compensation approach.
The main limitations of this study relate to the validity of using compensation payments to estimate the cost of some components in the Road Injury Cost Database, the accuracy of other data sources used in determining the unit cost estimates, and some assumptions that had to be made about the distribution of costs across body region and injury severity levels. The data used in developing the Road Injury Cost Database was the best obtainable data at the time of its construction and the assumptions were based on the best existing information. When better data becomes available, the unit cost estimates in the Road Injury Cost Database will be adjusted to incorporate the improved data.