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It is well known from field accident studies and crash testing that seatbelts provide considerable benefit to occupants in rollover crashes; however, a small fraction of belted occupants still sustain serious and severe neck injuries. The mechanism of these neck injuries is generated by torso augmentation (diving), where the head becomes constrained while the torso continues to move toward the constrained head causing injurious compressive neck loading. This type of neck loading can occur in belted occupants when the head is in contact with, or in close proximity to, the roof interior when the inverted vehicle impacts the ground. Consequently, understanding the nature and extent of head excursion has long been an objective of researchers studying the behavior of occupants in rollovers.

Vehicle motion prior to a rollover can influence an occupant's position in the vehicle. Lateral deceleration prior to a tripped rollover may cause the occupant to move outboard. This outboard motion may have several effects on the occupant such as, repositioning the occupant with relation to the seat and seat restraint, and allowing the occupant's head to travel further into the side curtain deployment zone. To reduce occupant lateral motion, the effectiveness of applying tension to the seatbelt was evaluated. The evaluation consisted of two test conditions simulating vehicle lateral motion prior to a trip using a Deceleration Rollover Sled [1]. The test conditions were designed to ensure a vehicle experiences a period of pure lateral motion before the onset of a lateral trip. A standard seat belt combined with various means of applying tension and activated at different times during the test were evaluated.

A tripped rollover is one of several types of rollover initiations. Developing a curtain airbag system for occupant protection in tripped rollovers requires the knowledge of the occupant kinematics prior to tripping. As a vehicle experiences lateral deceleration prior to the trip initiation, the unrestrained dummy head is already in motion and may be close to the vehicle interior or at the side glass plane. If the vehicle is equipped with a curtain airbag system, it may be difficult to trigger the curtain deployment prior to the dummy interacting with the vehicle side structure due to the degree of difficulty in discriminating between a roll and no roll situation early enough in the event. For such conditions, a curtain airbag restraint system should be designed so that it deploys and positions itself properly as the dummy head is approaching the side glass plane or in the deployment zone.