The pre-pretensioner will give a more gentle load distribution on the occupants chest in the event of a car crash. The device will tighten the seat belt as early as one tenth of a second before a likely crash, using a fast electrical motor.

The elimination of slack in the belt system can therefore start earlier – even before a crash – and the system can be made reversible. Consequently, it is possible to "strap in" the occupant more gently. It also makes it possible to tighten the belt as a precaution when it is difficult to predict whether there will be a crash or not. The new system will be especially effective in preventing occupants from being thrown forward during severe braking.