The original Malibu II study, conducted by Bahling et al, found that neck compression loading in rollover crashes is caused by the occupant moving toward the ground and therefore, roof crush was not causally related to the loading. Some have disputed this finding claiming that the occupant does not “dive toward the roof,” but rather, the roof “moves in” toward the occupant, and that roof deformation is the primary cause of cervical spine injuries in rollover crashes.
The original study included a detailed analysis of film and force transducer data for 10 Potentially Injurious Impacts (PII's). This paper presents an independent analysis of these 10 PII's and one additional PII. This analysis uses the film and transducer data to evaluate the timing of roof deformation and neck loading, the magnitude of roof deformation at the time of peak neck load, and the motion of the vehicle and occupants in the inertial reference system.
The data establish that the peak neck load occurs shortly after the roof-to-ground contact, and that there is 1.0-1.5 in. (2.5-4.0 cm) of roof crush at the time of peak neck load. This small magnitude of roof deformation occurs as the body of the vehicle moves toward the ground during the build-up of the neck load.
The roof at the location of the dummy's head was found to be in contact with the ground at the time of peak neck load for nine of the PII's. When the roof at the location of the head was not in contact with the ground at the time of peak neck load, the loading was the result of the roof panel experiencing a change in velocity as a remote part of the rollcaged roof contacted the ground.
Motion of the dummy and the roof in the inertial reference system establishes that the roof does not “move in” toward the occupant, but that the roof and the dummy's head both move toward the ground, that they stop when they contact the ground, and that the chassis of the vehicle and the torso of the dummy continue to move toward the ground, resulting in neck compression loads and roof crush. Therefore, no causal relationship exists between the vehicle deformation and the neck loading.