Whiplash, or soft tissue cervical injury, is a common injury incurred by occupants of passenger cars in rear-end collisions. Despite much investigation into the cause of such injury, no single mechanism describes it completely. Proposed criteria focus on the relative motions of the head and the thorax, while few case studies have been made on the motions of the cervical vertebrae. Recently, the human body finite element model called ”THUMS”(Total HUman Models for Safety) and the use of X-ray cineradiography devices by volunteers have accelerated the investigation into the motions of the cervical vertebrae.

Seats have been developed that are specially designed to reduce impact on the neck in rear-end collisions by simultaneously restraining the head and body of the occupant and controlling their motion relative to each other. We have developed a seat that also reduces local strain of the neck by preventing the rotation of the head, and that uniformly distributing the loads on the cervical vertebrae.

A finite element model was used to simulate rear-end collisions under the same conditions as sled tests using a BIO-RID II dummy, with a THUMS human model placed on our newly developed seat. Prior to the simulation, the validity of the THUMS was investigated by comparing its head and neck motions with those in experiments. The validated THUMS predicted a reduction of local strain in the neck on the newly developed seat.

Having succeeded in reducing both the injury values to the dummy and the local strain of the neck of the THUMS, we predict that our new seat design to help reduce whiplash injury.