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The traditional WIL (Whiplash Injury Lessening) concept seat has been further developed to achieve a 10-20% reduction in the severity of whiplash injuries.

The Active Headrest has been developed as an extension of the WIL concept seat. By adding the Active Headrest unit to the traditional WIL concept seat, a further 10 to 20% reduction in the value of neck injury index (Toyota neck injury evaluation index) can be projected(Figure 1).

Figure 1 Reduction on Neck Injury Index (in-house survey)

When the occupant's back presses against the seatback during a rear-end collision, a built-in lower unit instantaneously signals an upper unit through a cable. This trigger makes the head restraint move diagonally upwards in a span of only 0.03 of a second 2 (30 mm upwards, 25 mm forwards). The head restraint swiftly and securely catches the back of the occupant's head, thereby reducing the degree of impact to the occupant's neck and lessening the severity of any whiplash injury.

2: The physique, position and posture of the occupant inside the vehicle and other factor will affect this time.

The Active Headrest is the product of extensive research utilizing THUMS (Total Human Model for Safety) simulations.

Using THUMS, the virtual human model, as an essential part of development of the WIL concept seat showed that moving the headrest diagonally upwards, not just increasing the amount by which the headrest moves forward, cushions both the head and lower back at the same time and contributes to a further lessening of impact on the neck.