A Study of Occupant Ejection Mitigation in Side Impact Crashes

The National Highway Traffic Safety Administration (NHTSA) has identified ejection mitigation as a top priority, issuing a notice of proposed ruling making (NPRM) in December of 2009. The NPRM proposes a linear impact test that uses a featureless head-form to impact a vehicle's side windows' daylight opening at various positions. The test measures the excursion of the head-form beyond the plane of the window glazing. The intention is to evaluate the ability of a vehicle's ejection mitigation system, such as the curtain airbag or other vehicle features, to manage the impactor energy and limit excursion. The NPRM proposes a test conducted 1.5 seconds after the ejection mitigation countermeasure is deployed at an impact speed of 24 km/h with a mass of 18 kg (400 Joules). This test condition is intended to consider both rollover and side impact crashes. While the majority of the research published to date has concentrated on occupant ejections in rollover crashes, there is little published literature focusing on side impact crashes. The authors will present the results of a study in which computer modeling using a generic vehicle environment was used to estimate an ejection representative energy level for side impact crashes that can be employed for evaluating ejection mitigation systems. The effects of factors such as vehicle architecture and interior layout were considered in this study.