Automatic Emergency Braking for Pedestrians: Effective Target Population and Expected Safety Benefits

Automatic Emergency Brake (AEB) for pedestrians is a technology that automatically applies braking force to a vehicle when forward detection sensors determine that a collision with a pedestrian is imminent, thereby assisting in avoiding the collision altogether, or if it is unavoidable, reducing the impact speed of the crash and subsequently the risk of fatal/severe injury to pedestrians. The driver might be first notified about the danger by a tone or a visual warning or by an haptic feedback in the brake. If the driver does not act and if the impact is considered as inevitable, an automatic braking is applied. Notification step can also be skipped and the system brakes when the imminent collision is detected. Braking strategies vary across systems in terms of operating speeds range, adjusting the level of the braking force and the time when impact is considered inevitable. The value of deceleration is generally limited to 0.6 g. The aim of this study is two-fold: (1) Examine in which particular crash situations this kind of system is relevant. In France, pedestrian crashes account for 15% of injury crashes. However, there are a few considerations that might dramatically reduce this a priori aggregated target population: Performance of sensors varies across models and suppliers. A small range of different in-vehicle enhanced braking systems are currently available that involve differing activation processes and functionality, and are likely to provide varying benefits in terms of fewer crashes and mitigation of vehicle/pedestrian fatalities and serious injuries; and (2) Propose an evaluation of the expected safety benefits of such systems. A detailed analysis of pedestrian crashes was carried out with the help of European in-depth crash data as well as police reports. Results show that, pedestrian crashes happen more often in cities, in the daytime, whereas the pedestrian crosses the street. Expected effectiveness of AEB for pedestrians, if 100% of the fleet is fitted with a perfect system that never fails, would be a reduction of 15.3% of fatal pedestrian crashes and 38.2% seriously injured pedestrian crashes each year. These would amount to 1.3% and 3.8% of all fatal and serious injury crashes respectively that occur annually in France.