UK cost-benefit analysis: enhanced geometric requirements for vehicle head restraints

No regulatory test exists in Europe to assess injury risk in rear impacts. A number of vehicle accident and occupant injury studies indicate that low-speed rear impacts can lead to neck and back injuries causing long-term disablement and discomfort. These injuries are usually classified as having a low threat to life, but they are often associated with large societal costs. It is thought that design changes to seat systems and/or head restraints to improve their use and the occupant protection they offer could make a positive impact in mitigating injuries from rear impacts. Test procedures to assess the performance of seat and head restraint systems are being developed currently. As a first stage in the mitigation of injuries in low-speed rear impacts a static test of head restraint geometry is being developed by the European Enhanced Vehicle-safety Committee (EEVC) Working Group 20 ‘Rear Impact’. This report examines the cost-benefit ratio of controlling head restraint height and head restraint backset. Benefits are based on UK accident data the DfT willingness to pay model. The cost of long-term whiplash injuries to front seat occupants in the UK was estimated to be approximately £3 billion pounds annually, and potential casualty savings were calculated as a proportion of this cost. Injury mitigation and cost-benefit graphs were provided for different potential height and backset requirements, from which thresholds for each can be chosen. It should be noted that a static geometric head restraint requirement is a first step in mitigating low-speed rear impact injuries, and additional benefit may result from appropriate dynamic seat testing.