3Crash Safety Division, Chalmers University of Technology
Since more occupants are using rear seats of vehicles, a better understanding of priorities for rear occupant protection is needed as future safety initiatives are considered. A two-part study was conducted on occupant injuries in rear seating positions. In Part I, adult and teenage occupants ≥13 years of age are investigated. In Part II, children aged 4-12 years old and toddlers and infants aged 0-3 are studied separately because of the use of infant and child seats and boosters involve different injury mechanisms and tolerances.
The objectives of this study on adult and teenager, rear-seated occupants (≥13 years old) are to: 1) review accident data, 2) identify the distribution of rear occupants, and 3) analyze injury risks in various crash modes, including rollovers, frontal, side and rear impacts. Three databases were investigated: NASS-CDS, GES and FARS. Results indicate that there is <25% probability of having a rear occupant of any age for every driver involved in any of the databases, and the probability is increasing with accident year. With respect to crash type, the risk for rear occupants to be killed was highest in side and rear impacts and in rollovers, while the rate for serious injury (MAIS 3+) was highest in rollovers and side impacts. However, in comparison to drivers and the right-front passengers, the fatality risk and serious injury rate were greatest in rear impacts.
63% of the rear occupants were unbelted in FARS, while about 40% were unbelted in NASS. Unbelted adult occupants had a higher risk of serious injury than lap belted and lap/shoulder belted occupants. In the weighted data, front seat occupants have a lower rate of serious injury than 2nd and 3rd row seat occupants. However, lap/shoulder belted occupants have a lower risk to be seriously injured in the 2nd and 3rd row seat.
For the lap and shoulder belted adult 2nd rear seats occupants, thoracic injuries were most common. They often resulted from contact with the seatbelt. Current field injury data and the literature point to the following possible priorities for adults and teenagers using rear seats: 1) load-limiting belts with cinching and good restraint geometry, 2) EA material for the seatback, side interior and B-pillar, 3) reduced contact velocity with seatback, side interior and B-pillar, 4) improved containment with inflatable side curtains and laminated side glass, and 5) possible technologies such as inflatable belts.