The combined effect of vehicle frontal design, speed reduction, autonomous emergency braking and helmet use in reducing real life bicycle injuries

Vulnerable road users as bicyclists and pedestrians account for a significant share of fatalities and serious injuries in the road transport system. Traditionally, the protection for bicyclists has been addressed by speed management and separating vulnerable road users from motorized traffic. Also, the use of bicycle helmet has been prompted and regulated in some countries. Pedestrian protection by improving the car fontal design has been around since the late 1990s and has proven to be effective in reducing injury risk on pedestrians (Strandroth et al., 2011) as well as on bicyclists (Strandroth et al., 2014). Pedestrian detection with Autonomous Emergency Braking (AEB) has also been introduced on the market to prevent and mitigate pedestrian and bicyclist injuries. The purpose of this study was to evaluate the effect of the different interventions promoting safety for vulnerable road users, and an additional purpose was to look at the combined effect of the interventions. Swedish emergency hospital reports from approximately 2000 bicyclists and 1200 pedestrians between Jan 1st 2003 and March 2014 were included in the study. Hospital reports including injury diagnosis were combined with police data and the vehicle registry in order to obtain detailed vehicle information. Euro NCAP pedestrian test score, speed limit restriction and helmet use was correlated with real-life pedestrian and bicyclist injuries. The results showed that on pedestrians, large injury reductions were found comparing low scoring cars (1-9 p) in the Euro NCAP pedestrian test to high scoring cars (>18 p). Also for bicyclists significant injury reductions were found. Focusing on bicyclist's injury level, large reductions were found on all body regions, with the highest reduction on head injuries. The effect of speed limit restriction showed few statistically significant results, although across both pedestrian and bicyclist injuries the trends showed overall small but positive effects. The effect of helmet use on bicyclist injuries was investigated both on individual level and on head injury level. Helmet showed to significantly reduce the risk of head injuries. However, on individual level, the results were quiet conflicting, and only on mRPMI10+ level a positive and statistically significant reduction was found. The calculated combined effect of speed-reduction, helmet-use and car frontal design was 79%. Also, preliminary calculations, based on a limited number of cases, and including both bicyclists and pedestrians, showed that when adding the effect of AEB, the risk of long-term impairment decreased by more than 90%.