Pediatric and adult rear passenger kinematics in manual and automated emergency braking

Up to 80% of crashes are preceded by pre-crash maneuvers such as emergency braking. Precrash maneuvers, which may avoid or mitigate crashes, also may influence passenger kinematics and lead to less optimal positioning if a subsequent crash occurs. Previous research has documented driver kinematics during automatic braking. Yet, passenger response to automated emergency braking is less understood. This is also relevant for those in the rear seat who may not anticipate the braking event. Thus, we compared rear passenger kinematics for pediatric and adult human volunteers in driver-applied manual emergency braking (MEB) and automated emergency braking (AEB) via closed track testing. 18 participants (5 adults (age 22.0 ±1.9 years), 7 teens (age 14.9 ±1.2 years), 6 children (age 10.8 ±1.6 years)) were seated in the rear right passenger seat of a modern 4-door sedan. Steady-state head and sternum displacement and peak rate of change of displacement were compared across maneuvers. As a method to compare outcome measures across age groups, displacements were normalized to participant seated height and rate of change in displacement was normalized to participant mass. For MEB an average deceleration of 0.96g was achieved compared to 0.77g for AEB. Mean head and sternum displacement was greater (p=0.003, p=0.006, respectively) during MEB (15.0 ±3.4 cm, 8.1 ±1.9 cm, respectively) than AEB (10.9 ±4.9 cm, 6.1 ±2.4 cm, respectively). Mean head and sternum peak rate of change was greater (p<0.001 for both) during MEB (92.2 ±11.3 cm/s, 854.6 ±10.9 cm/s, respectively) than AEB (37.6 ±15.5 cm/s, 20.1 ±8.4 cm/s, respectively). Children exhibited greater normalized peak head rate of change (p=0.03, 1.43 ± 0.7) than adults (0.96 ± 0.50). The reduced excursion and velocity of movement found with the automated emergency braking system demonstrated the potential for AEB to mitigate occupant motion during emergency braking across all age groups.