The Dynamic Test Procedure

The seat is placed on our Hyper-G test sled and accelerated to 10 mph (16 km/h) in a tenth of a second, recreating the forces endured by an occupant in a typical low speed crash. The accelerations and forces imparted to the crash dummy are recorded for detailed analysis. The test procedure assesses three important criteria and combines them into a final single rating. The first two components are combined together to form the 'dynamic' rating. These are:

• The seat assessment criteria, which is based on the ability of the seat to absorb energy by measuring the acceleration of the dummy and by measuring the time it takes until the head restraint can support the dummy's head
• An assessment of the forces imparted to the neck of the dummy. The requirement is to limit any values to well below those which may injure people

Finally, the measurement of the geometry of the head restraint is added to ensure that occupants taller than the average sized test dummy are also protected. This produces a final overall rating which we publish as 'Good', 'Acceptable', 'Marginal' or 'Poor'.

These ratings only allow a comparative assessment of a seat's ability to protect its occupant in a typical crash. They cannot be used as a guide to whether a particular injury is more or less likely, since we still do not know enough about the mechanisms of whiplash injury to state this confidently. Thatcham only evaluate front seats at present, as the majority of injuries occur to front seat occupants. The IIWPG (International Insurance Whiplash Prevention Group) standard requires that the seat must have a minimum level of geometric protection. Therefore, seats that have 'MARGINAL' or 'POOR' geometry do not get tested, automatically earning a 'POOR' rating by default.

IIWPG Test Protocol v2.5 (pdf)