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Rear end collisions account for approximately $9 billion annually in the United States alone. These types of collisions account for nearly 30% of all vehicle impacts making them the most common type. Soft tissue injury to the neck (i.e. “whiplash”) is typically associated with this type of collision due to the occupant dynamics of the passengers in the struck vehicle. At low relative impact velocities, whiplash-type injuries are known to occur but are typically attributed to: 1) improper seat adjustment, 2) an “out-of-position” event, or 3) a low injury threshold due to age, gender, etc. In high impact collisions, both whiplash and occupant ejection can take place, the latter placing far greater risk of injury not only to the front seat occupant, but also to any rear seat passengers as well. The automobile seating system is the predominant safety device employed to protect the occupant during these types of collisions.

Improving the safety of vehicle occupants has gained increasing attention among automotive manufacturers and researchers over the past three decades. Generally, more recent vehicle safety improvement and injury prevention techniques could benefit from accurate knowledge of the occupant presence, characteristics, and/or position within the interior space of the vehicle. There is increased potential for injury mitigation systems to be applied more effectively if the proximity of the occupant to restraint devices is obtained in real-time during vehicle operation. A particular application is the position of the head relative to the head restraint for mitigating neck injuries from rear end impacts, which has led to the development of “active” head restraint systems.

The seat is the most important safety device available to vehicle occupants during rear end collisions, and thus proper design and structural integrity of the seat under expected impact loading is essential. The objective of the current research work is to increase our understanding of the design requirements for seat performance in relation to injury producing collisions, and to examine how various seat design parameters affect both structural integrity and occupant protection. A numerical model-based parametric study was developed based upon the 2002 GM Grand Am seat. The parametric study utilizes a 50th percentile male dummy, applies the FMVSS 202 standard crash pulse to selected structural variations of this seat, and then utilizes the neck injury criterion (NIC) and neck displacement criterion (NDC) to assess the likelihood of injury.