Rear-seat occupant demographics in rear impacts: Analysis of NASS-CDS.

Purpose: This study analyzes field accidents to identify rear-occupant exposure and injury by crash types. Occupant demographics and injury were assessed by body region and crash severity to understand rear-occupant injury mechanisms in rear crashes.

Methods: The exposure and serious-to-fatal injury was determined by crash type for non-ejected second- and third- row occupants in 1994+ MY vehicles using 1994-2015 NASS-CDS. Selected occupant demographics and serious injury distributions were assessed over a range of delta V for rear crashes.

Results: Rear crashes accounted for 8.7% of exposed and 5.4% of serious-to-fatally injured rear-seat occupants. On average, rear-seat occupants were 14.3 ± 1.5 years old (median 10.3, 90 CI 0.08-29.6), weighed 44.7 ± 2.6 kg (median 44.4, 90 CI 7.9-81.7) and were 130.3 ± 4.1 cm tall (median 141.4, 90 CI 67.3-178.4). With serious injury, the average rear occupant was 18.1 ± 5.8 years old (median 13.1, 90 CI 0.0-47.2), weighed 42.6 ± 10.7 kg (median 31.4, 90 CI 7.0-82.4) and was 120.6 ± 15.4 cm tall (median 145.4, 90 CI 48.8-174.1). More than 72% of rear-seat occupants were in delta V less than 24 km/h. Less than 2% were in delta V 48 km/h or greater. The overall rate of serious-to-fatally injured (MAIS 3 + F) was 0.73% ± 0.37%. For serious-to-fatally injured rear-seat occupants, the average delta V was 37.4 ± 3.1 km/h (median 29.8, 90th CI 28.6-62.1). None were involved in delta Vs less than 24 km/h, about 78% were in a delta V between 24-48 km/h and 22% were in a delta V of 48 km/h or greater. Head and chest were most commonly injured, irrespective of crash severity.

Conclusions: The height and weight of a 10-year old and 5 Hybrid III ATD are representative of the average rear-seat occupant involved in rear crashes based on NASS-CDS. Crash tests with a delta V of between 30 and 37 km/h represent the typical collision causing serious-to-fatal injury.