Methodology to Evaluate the Flail Space Model by Using Event Data Recorder Technology

The flail space model, which was developed in the 1980s, has become the standard method for estimating occupant risk in full-scale crash tests involving roadside safety features. The widespread availability of air bags and increased seat belt usage rates in today's vehicle fleet, however, raise serious questions concerning the validity of the model. Recent installation of event data recorders (EDRs) in a number of late-model vehicles presents a different perspective on the assessment of the validity of occupant risk based on the flail space model. EDRs are capable of electronically recording data such as vehicle speed, brake status, and throttle position just before and during an accident. Of particular interest is the EDR's ability to document the deceleration of a vehicle during a collision event. A methodology using EDR data to investigate the capability of the flail space model to predict injury to air bag-restrained occupants and results of a preliminary analysis based on implementation of the developed methodology on a limited data set are presented. Most of the analysis is limited to the occupant impact velocity because of insufficient data for evaluation of the occupant ridedown acceleration. The longitudinal occupant impact velocity was found to be a good predictor of overall injury, chest injury, and, to a lesser extent, lower extremity injury. For the head and upper extremity body region, the longitudinal occupant impact velocity is a weak predictor of injury.