Assessing the benefit of the brake assist system for pedestrian injury mitigation through real-world accident investigations

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The compulsory fitting of the brake assist system (BAS) for new vehicles in the European Union has been recently established by Regulation (EC) 78/2009 to enhance the protection of pedestrians. This paper describes the main findings of a coordinated study performed by four Spanish Safety Research Centres aimed at assessing the potential influence of the BAS in vehicle–pedestrian collisions through the reconstruction of real-world accidents that occurred in three different cities of Spain. A total of 139 vehicle–pedestrian collisions were investigated in-depth following a common methodology, including on-the-spot data collection, analysis and reconstruction to estimate the collision speed and the pedestrian kinematics. A specific procedure was defined to emulate, through computer simulations, the performance of the BAS acting together with the antilock braking system (ABS). The benefit was assessed in terms of both collision speed and Injury Severity Probability (ISP) by comparing the reduction of their values from the real conditions to the virtual BAS+ABS simulations. The pedestrian ISP was estimated, depending on the collision speed and the head impact point, using a specific application that calculated its value based on the results of headform impact laboratory tests. The ISP values obtained in both conditions were compared. The findings show that while implementing the BAS+ABS would not have prevented the collision in most of the cases, it would have reduced their consequences in terms of the estimated ISP. It was also found that in few cases, a small reduction in the collision speed would increase the head injury severity.