1999–2015 NASS-CDS data were used to investigate the risk for Maximum Abbreviated Injury Scale (MAIS) 3+F injury in rear crashes involving 2000+ model year vehicles. Front-outboard occupants 15 and older were included without ejection (ejection = 0). The frequency of serious-to-maximum injury was assessed by body region. The distribution of injury sources was then queried for AIS3-6 head, neck and spine injury. Overall, frontseat occupants had the lowest risk for serious injury in rear impacts compared to other crash types. The risk was 0.497 ± 0.120%. There were 2.76 AIS 3+ injuries per serious-to-fatally injured occupant on average. Most serious injuries occurred to the head from contact with front (44%), rear (36%) and side (12%) interior components. The B-pillar, head restraint and seatback were common sources.

An in-depth review of electronic cases was conducted involving front-seat occupants with serious head or spine (AIS3-6) injury from contact with the B-pillar, head restraint and/or seatback. The individual cases were reviewed for damage to the vehicle and interior. There were 4 unweighted cases involving a serious-to-maximum (AIS 3+) head injury due to seatback contact;​ all were from intrusion pushing rear structures forward into the front-seat occupant. Three of 4 occupants were belted. There were 18 unweighted front-seat occupants with a serious-tomaximum (AIS 3+) neck/spine injury related to the seat and seatback. Nine occupants were injured by intrusion of rear structures, which were deformed forward into the occupant. Three occupants were injured by “diving” into the rear seatback causing T-spine fractures.

While the risk of serious injury is low in rear impacts, there are injuries to the head, neck and spine. Intrusion was a significant source for AIS 3-6 head, neck and spine injuries. The B-pillar adjacent to the occupant was a common source of injury. NASS-CDS identified no case of AIS 3+ head injury by “diving” type motion but found AIS 3+ T-spine fractures by “diving” into the rear seatback by belted occupants.

This study provides insight into interior contacts associated with serious injury to front-seat occupants in rear crashes. It identified head restraint, seat and B-pillar as common injury sources. A majority of cases involved components lateral to or forward of the front occupant. Head injury from a “diving” mechanism was not observed, but T-spine fractures occurred with belted occupants.