WHIPS, or Whiplash Protection System, is a system of protection against automotive whiplash injuries

Whiplash (medicine)

Whiplash is a non-medical term describing a range of injuries to the neck caused by or related to a sudden distortion of the neck associated with extension. The term "whiplash" is a colloquialism...

 introduced by Volvo

Volvo Cars

Volvo Car Corporation, or Volvo Personvagnar AB, is a Swedish automobile manufacturer founded in 1927, in Gothenburg, Sweden. It is owned by Zhejiang Geely Holding Group. Volvo was originally formed as a subsidiary company to the ball bearing maker SKF. When Volvo AB was introduced on the Swedish...

 in 1999 in the Volvo S80

Volvo S80

The Volvo S80 is a mid-size executive saloon/sedan from Swedish automaker Volvo Cars, and was introduced in 1998 to take the place of the rear-wheel drive Volvo 960/S90 saloons in the model range. The Volvo S80 was built at the Torslanda Plant in Gothenburg, Sweden. Unlike most Volvo models, it...

.

In the WHIPS equipped seat, the entire backrest is designed to help protect the front occupant's neck

Neck

The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...

 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. 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

Insurance Institute for Highway Safety

The Insurance Institute for Highway Safety is a U.S. non-profit organization funded by auto insurers, established in 1959 and headquartered in Arlington, Virginia. It works to reduce the number of motor vehicle crashes, and the rate of injuries and amount of property damage in the crashes that...

 (IIHS) rates head restraint and seat designs and the 2009 EuroNCAP

EuroNCAP

The European New Car Assessment Programme is a European car safety performance assessment programme based in Brussels and founded in 1997 by the Transport Research Laboratory for the UK Department for Transport and backed by several European governments.-History and activities:Euro NCAP is a...

 5 star safety testing now includes whiplash protection as part of the testing program.
Saab Automobile AB was first with introducing active headrestraints.