A Study of Occupant Ejection Mitigation During Rollovers for Front Row Occupants

As a part of its ejection mitigation research, the National Highway Traffic Safety Administration (NHTSA) has proposed 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 countermeasures, such as the curtain airbag or other vehicle features, to manage the impactor energy and limit excursion. However, at this time NHTSA has not yet established the performance criteria for the excursion. Additionally, there is no clear agreement on the energy level to be used for ejection mitigation testing. The agency has considered three energy levels for the head-form impact: 178, 280, and 400 Joules [ 9 ]. This paper discusses the results from computer modeling used to study an ejection representative energy level that can be employed for evaluating ejection mitigation systems. Additionally, the authors will present a parameter study in which the stiffness of a curtain airbag has been optimized considering both the NHTSA's ejection mitigation research test method as well as side impact performance.