Head Contacts in Rear-seated Pediatric Occupants When the Front Seat is Reclined in AEB Scenarios

Principal Investigator: Valentina Graci, PhD, Children's Hospital of Philadelphia


Interest in reclined passenger seating is growing as a feature of future autonomous vehicles. However, there is a lack of research regarding the safety of rear-seated occupants. With a reduction in space between rear-seated occupants and reclined front seats, head injuries may occur. This study investigated head contacts with a reclined front-row seatback during automated emergency braking (AEB).

Using computational modeling, we simulated a front seat positioned at several seat track positions with three different recline angles: 25 degrees (nominal position in today’s vehicles), 45 degrees, and 60 degrees. First, we examined head excursion and contact of 10- and 6-year-old rear-seated child passengers in three different restraint conditions: a seat belt, a low-back booster seat, and a high-back booster seat during an AEB pulse. Second, we investigated changes in head contact velocity across four exemplar AEB pulses.


The models showed a significant amount of head contact between the rear-seated child and front row seatback. We found a correlation between head impact velocity and jerk of the AEB pulse. This outcome demonstrates that different AEB pulses may result in different kinematics of the occupant, placing them in different pre-crash positions with the potential for injuries.


Our findings show that child occupants seated behind reclined seats may be at risk of head contact during AEB. When car manufacturers consider placing reclined seating configurations in autonomous vehicles, rear passenger safety should be taken into account.

An important next step is to consider revisiting standards set for AEB, given new front seating positions (e.g., reclined). The current standard only requires that the vehicle reduces speed in front of an obstacle; it does not put boundaries on how that speed reduction is obtained. Defining more measures, such as acceptable jerk level, could be helpful in protecting occupants. Additional testing is required to determine the amount of space needed between a rear passenger seat and a reclined front seat to avoid head contact.

head contacts in rear seat
Simulation of a 6-year-old occupant model on low back booster: (left) initial position, (right) head contact with front seat reclined at 60 degrees and a track position of 50mm during AEB.


Declan Patton, PhD, Children’s Hospital of Philadelphia; Jalaj Maheshwari, MSE, Children’s Hospital of Philadelphia; Kristy Arbogast, PhD, Children’s Hospital of Philadelphia

IAB Mentors

Emily Burton, American Honda Motor Co., Inc.; Jennifer Stockburger, Consumer Reports; Emily Thomas, Consumer Reports; Mark LaPlante, Graco Children’s Products Inc.; Jerry Wang, Humanetics Innovative Solutions Inc.; Erin Hutter, National Highway Traffic Safety Administration; Schuyler St. Lawrence, Toyota USA