The safety effect of increased pedestrian protection, autonomous emergency braking for pedestrians and bicyclists on passenger cars, and speed management

The overall objective of this paper was to estimate the effect of increased pedestrian protection and speed management to reduce serious injuries among pedestrians and bicyclists. More specifically, the aim was to estimate the injury mitigating effects of the following interventions: AEB with pedestrian and bicyclist detection, Euro NCAP pedestrian test score, Active Bonnet, Traffic calming at pedestrian and bicycle crossings, and additionally, the combined effect of the above-mentioned treatments. The main source of data was the Swedish traffic data acquisition system, where information of road traffic crashes between passenger cars and pedestrians or bicyclists for the period January 2003–December 2022 was obtained. Cars with optional fitment of AEB systems were identified, and the license registration number was used to access individual car equipment lists to identify whether the vehicle was equipped with AEB with pedestrian and/or cyclist detection. Information about traffic calming at pedestrian and bicycle crossings was obtained from the Swedish Transport Administration. The injury metric used was risk of permanent medical impairment (RPMI) of at least one percent and ten percent. RPMI captures the risk of long-term medical impairment based on a diagnosed injury location and Abbreviated Injury Severity score. The relative difference between the mean values of RPMI (mRPMI1% and mRPMI10%+) was calculated and tested using an independent two sample t-test which was conducted for unequal sample sizes and variance. Pedestrian mRPMI10%+ was reduced by 34%–44% in speed zones 10–50 km/h comparing the group struck by cars equipped with AEB with pedestrian detection compared to the group struck by cars without the system. However the reduction was only significant at 90% level. The pattern was similar also for mRPMI1%+. For cyclists, the mRPMI10%+ was reduced by 35% at speed zones 10–50 km/h. For crashes within +/- 20 meters from a pedestrian or bicycle crossing, the AEB system reduced 60% (p = 0.05) of pedestrians mRPMI10%+ at crossings with good safety standard compared to crossings of poor safety standard. The comparison of cars with poor performance (1–9 p) in the NCAP pedestrian test and cars with a high score (28–36 p) showed that pedestrian mRPMI10%+ was reduced by 48% (p < 0.01) across all speed limits, and by 64% including only those aged ≤ 64 years. For bicyclists, a significant reduction of cyclist mRPMI10%+ was found comparing low scoring cars to h