Review of flail-space's lateral impact velocity criterion for thoracic impacts

Abstract

ABSTRACTThe simplified point mass, flail-space model was introduced in 1981 and is currently used in the United States, Canadian, Australian, and New Zealand road safety barrier and fixtures standards as a method of assessing vehicle occupant injury risk in certification crash tests when an instrumented anthropomorphic crash test dummy is not used. Maximum and preferred flail-space threshold impact velocities and accelerations of an unrestrained occupant are specified for longitudinal (frontal) and lateral (side) impact in the standards. The longitudinal impact velocity component of the flail-space model has been compared with impact velocities from real-world frontal crash data. However, the lateral velocity component has yet to be compared with impact velocities from any side impact tests or real-world injury crash data. This current study assesses the relationship between injury severity and impact velocities from cadaveric lateral thoracic impact tests and relates this to the maximum and preferred lateral velocities as recommended in the flail-space model. The following data from previous thoracic lateral impact cadaver tests were collated: impact velocity, cadaver age, cadaver mass, impact wall padding thickness, impact test method, and resultant Abbreviated Injury Scale (AIS) level. Multiple logistic regression analysis was used to determine the significant variables in predicting AIS 3+ and AIS 4+ injuries. Single variable regression analysis was then performed to determine a relationship between lateral impact velocity and AIS 3+ and AIS 4+ injury level. From the results, the current flail-space model's preferred lateral velocity used in the road safety barrier standards was found to be high and a lower preferred threshold of 6.4 m s−1 is proposed.