There are several hypothesizes regarding the cause of "whiplash injuries”. Loading to structures in the neck has been shown to occur during the whiplash motion sustained in a vehicle crash. Highly specified crash test dummies are used.in car seat evaluation today. Tests performed with these dummies provide values which can be compared with thresholds known to pose a risk of an average male occupant sustaining an injury.
Loads to occupants can be assessed using these dummies. Below are some examples of relevant information for the evaluation of car seats:
- Acceleration of the head and chest
- Forces between head and neck
- Bendingmoments between head and neck
Neck Injury Criterion (NIC), a calculated criterion with respect to acceleration of the head and lower neck
- Nkm, a calculated criterion in respect of neck shear forces, neck flexion and extension moments
- Rebound velocity of the head following the impact on the head restraint
- Shear force between head and neck
- Tension force between head and neck
- Acceleration of the lower neck, e.g., first thoracic vertebra
- Duration between the start of the collision and the moment the head makes contact with the head restraint
A suggestion to assess different thresholds for female occupants has been established during the ADSEAT project. Investigations revealed that most values need to be modified to take into account different anthropometry. An initial reduction of 40 % in reference values for Nkm, and a reduction of 20% for the NIC was suggested.