Vehicle and Occupant Responses in a Friction Trip Rollover Test

Methods: A flat dolly carried a Saab 9-3 sedan laterally, passenger-side leading to a release point at 42 km/h (26 mph) onto a high-friction surface. The vehicle was equipped with roll, pitch and yaw gyros near the center of gravity. Accelerometers were placed at the vehicle center tunnel, A-pillar near the roof, B-pillar near the sill, suspension sub-frame and wheels. Five off-board and two on-board cameras recorded kinematics. Hybrid III dummies were instrumented for head and chest acceleration and upper neck force and moment. Belt loads were measured.

Results: The vehicle release caused the tires and then wheel rims to skid on the high-friction surface. The trip involved roll angular velocities >300 deg/s at 0.5 s and a far-side impact on the driver’s side roof at 0.94 s. The driver was inverted in the far-side, ground impact. Head impact and torso deceleration resulted in 8.75 kN neck compression load with about ½″ of roof deformation, <¼″ vehicle cg displacement and >5 g vehicle deceleration. The vehicle came to rest on its roof after 1½ rolls.

Conclusion: The friction rollover involved centrifugal accelerations moving the driver’s head to the roof at ground impact. The driver was inverted and the torso dove toward the ground causing high neck compression loads. This test confirms the conclusions of Malibu II and CRIS testing that belted occupants can experience neck loads before much roof deformation. This test involved a modern vehicle with a strong roof. Increasing roof strength would not reduce neck loads; reclining the head-neck-torso angle before the far-side roof impact seems a more reasonable approach to improving safety.