Recently various researchers have attempted to clarify the mechanism of whiplash injuries, but the mechanism is not yet wholly understood. This is because researching tests are difficult to reproduce actual rear-end automobile accidents.

To solve this problem, we made experimental and numerical analyses.

First of all, we developed a new biomechanical cervical model named as ”K-D neck model” to reproduce human neck movements at low-speed rear-end collisions. Shear displacements in the plane of the intervertebral disks were observed.

Secondary, in order to verify the biomechanical fidelity of the K-D neck model, numerical analyses using finite element models with both active and passive muscle elements were conducted to compare among each lateral head displacement of the cadaver, the volunteer and the K-D neck model.

To reduce whiplash injuries, the new headrestraint system equipped on a car seat was developed. The headrestraint swings forward after low-speed rear-end collisions. By the sled tests, we measured the neck’s lateral and longitudinal cervical movements in every 1 millisecond, and observed that the faster support of the dummy head was effective to reduce both lateral and longitudinal displacements between each cervical vertebra.