WHIPS, or Whiplash Protection System, is a system of protection against automotive whiplash injuries introduced by Volvo in 1999 in the Volvo S80.
In the WHIPS equipped seat, the entire backrest is designed to help protect the front occupant's neck in a case of a rear impact.
According to a Volvo engineer:
The seatback moves together with the occupant in a way that is similar to catching a ball gently, while the head restraint remains rigid to support the neck
WHIPS equipped seats have a piece of metal inside the backrest that absorbs energy in case of rear end collision, reclining the headrest a few centimeters. The metal piece should be replaced after the event[1]. The main energy is absorbed via a virtual pivot at the base of the seat - mechanism allows the seat to move around the occupants actual hip joint while moving rearward to absorb additional energy.
WHIPS is standard within front seats of Volvo vehicles since 1994, with Volvo S80 being the only car in the world with WHIPS rear passenger headrests also. Similar front seat technology is now found in many Japanese and European vehicles.
Note: the Insurance Institute for Highway Safety (IIHS) rates head restraint and seat designs and the 2009 EuroNCAP 5 star safety testing now includes whiplash protection as part of the testing program. Saab Automobile AB was first with introducing active headrestraints.