Nearly 37 percent of traffic fatalities are pedestrians in Japan. More than half of them are involved in crashes when crossing roads. It may be difficult to stop the vehicle if a pedestrian suddenly appears from the roadside. Automatic Emergency Braking (AEB) was developed to help avoid collisions and to help mitigate collision severity. The benefit of AEB is usually assessed in laboratory tests following the prescribed protocols. In the real world, there may be various scenarios in which crossing pedestrians are at risk of condition. Previous studies tried to estimate the benefits of AEB in realistic conditions. One approach was to use computer simulation. In this study, functions of AEB were replicated in the computer simulation. The benefit of AEB was estimated by comparing the equivalent cases with and without AEB.

Precrash simulations were conducted to estimate the effect for collision avoidance with AEB. A base model was generated to replicate the scenario where a pedestrian crosses the road in front of a vehicle. The 17,000 models for the variety study were prepared for the precrash simulation changing the walking speed, walking direction, the vehicle speed and its lateral position in the lane.
After precrash simulations, crash simulations were conducted to estimate the effect of injury mitigation effect when AEB activates. The collision scenarios were same as the results of the precrash simulations. The 225 crash simulations were conducted and the results were utilized to develop HIC15 prediction model. The ranges of paramaters were defined as they can include all the collision conditions in precrash simulation. The prediction model was to predict HIC15 without conducting detailed crash simulations.

Our precrash simulation showed that 13,946 out of 17,000 cases did not lead to collisions regardless of with or without AEB. Collision occurred without AEB in 3,054 cases. In 2,563 cases out of the 3,054 cases, collisions were avoided when AEB activated. However 491 collisions occurred even with AEB. Thus, the benefit of AEB in collision avoidance was estimated at 84%. The collision speed ranged from 10km/h to 60km/h without AEB while it did not exceed 50km/h with AEB.
Our estimation of the fatality rates(HIC15 value > 700) were 4.0%(without AEB) and 1.0%(with AEB) respectively. Thus, the benefit of AEB in fatarity rate was estimated at 75%.