The Insurance Institute for Highway Safety rates vehicle seat/head restraint designs as good, acceptable, marginal, or poor using a protocol by the Research Council for Automobile Repairs’ International Insurance Whiplash Prevention Group (RCAR/ IIWPG). Studies of insurance neck injury claim rates for rear impact crashes show that vehicles with seats rated good have lower claim rates than vehicles with seats rated poor, but the relationship between acceptable/ marginal ratings and claim rates is less clear.

To better understand the relationship between measured neck injury criteria and injury claim rates, a series of rear impact crash tests was conducted to determine the influence of crash pulse, as dictated by vehicle structure, on the performance of seat/head restraints. The role of head restraint adjustment also was examined by comparing BioRID responses in the driver position, with the restraint adjusted according to the RCAR/ IIWPG protocol, and in the front passenger position, with the restraint adjusted to its lowest position. In an attempt to match the severity of the RCAR/IIWPG crash pulse, vehicles were struck by a flat rigid barrier to create a velocity change of 16 km/h (10 mi/h).

Four small cars with rated seat/head restraints and varying real-world neck injury claim rates were selected. The 2006 Honda Civic and 2005 Chevrolet Cobalt both received good ratings in the RCAR/ IIWPG sled test, but the Civic had a relatively low neck injury claim rate compared with the Cobalt. The 2006 Saturn Ion and 2005 Ford Focus both received marginal ratings in the sled test, but the neck injury claim rate for the Ion was comparable with that for the good-rated Civic, and the Focus had the highest neck injury claim rate among the vehicles tested.

BioRID response ratings for the driver position matched the sled test ratings for the Cobalt and Focus but were one rating level lower for the Civic and Ion. BioRID response ratings for the passenger position were the same as those for the driver position for all vehicles except the Cobalt, which was one rating level lower. The findings suggest that changing the RCAR/ IIWPG protocol to include vehicle specific crash pulses and/or changing the restraint setup would not improve the relationship between seat/head restraint ratings and neck injury claim rates. Furthermore, examination of additional BioRID injury metrics not currently assessed under the protocol does not help explain real-world neck injury claim rates and does not support changing the current evaluation criteria. Additional research is needed to determine whether vehicle underride/override alters vehicle accelerations in a way that makes crash tests more predictive of neck injury claim risk in rear-end collisions.