The side impact burden of Road Trauma: Identifying safety and clinical priorities to improve injury outcomes

Injury and mortality from side impact collisions are over-represented and under-researched compared to frontal collisions. Identifying the vehicle, crash, occupant, and clinical priorities is an essential and strategic step towards reducing the burden of road trauma. Methods: Side impact airbags are a new rapidly evolving technology designed to protect an occupant's head and/or thorax when struck on the near-side in a side impact collision. The effectiveness of each category and each type of side airbag, their ability to reduce injury or death at different speeds, and for different striking vehicles was analysed using data from the Monash University Accident Research Centre's In-depth Database (MIDS) in Australia and the National Automotive Sampling System (NASS) in the United States. An in-depth analysis of the influence of vehicle characteristics and geometry in side impact collisions and the risks of thoracic injuries (including death) and hospital length of stay (LOS) was further undertaken using data from the NASS system in the United States. A total of 5,880 cases were examined in-depth over several studies for passenger cars where an occupant was directly struck on the near-side. The data was presented using descriptive statistics, multivariate linear regression models, t-tests and chi-square tests, and Q-Q Plots to test normality. Results: Compared to no side impact airbag, Curtain airbags reduced the mean Abbreviated Injury Score (AIS) - the average of the three highest injury severity scores (meanAIS is an equal and interpretable version of the New Injury Severity Score) - by 41.20% p<0.0001. Inflatable Tubular Structures reduced the overall meanAIS by 35.40% p<=0.003, seat combination airbags by 27.17% p<=0.037 and thorax only airbags by 23.36% p<=0.001. Differences were observed when the striking vehicle was a four-wheel-drive and at collision speeds greater than 40 km/h however low case numbers and statistical power indicate those results should be interpreted with caution and as preliminary pending further research. Overall meanAIS was increased for passenger car occupants in near-side side impact collisions when struck by a four-wheel-drive (28.66% p<=0.01) compared to another passenger car. Four-wheel-drives were statistically more likely to cause maximum intrusion above the belt line and result in significantly greater thoracic and head and neck injuries. Near-side occupants that were impacted above the belt line had significantly greater average hospital LOS. Conclusion: Preliminary results indicate that side impact airbags reduce the overall meanAIS for near-side occupants in side impact collisions, with variations in performance depending on airbag type, however, their individual effectiveness in certain crash types remains unclear. Four-wheel-drives significantly increase the overall meanAIS to passenger vehicles. Future policy to strengthen side-structures of vehicles, improve vehicle incompatibility, financial disincentives for four-wheel-drive owners, and improvements to pre-hospital clinical management and guidelines should be prioritised to reduce the number of serious injuries and deaths from road trauma. Keywords: Side Impact; Trauma, Four-wheel-drive; Accident; Injury; Intersection; Vehicle; Airbags; Side Impact Airbags; Curtain Airbags; Pre-hospital; Crash Costs; Traumatic Brain Injury, Thoracic Injury