Autoliv says it has developed a new high performance reversible pre-pretensioner system for seatbelts that resets itself automatically after triggering, enhancing safety in multiple impact collisions.

The company says that during a multiple collision impact, the high performance system will pull back the occupants during the usually softer first impact to allow more optimum protection from the airbags and seatbelts in secondary impacts.

Autoliv presented the system at the 21st Conference Enhanced Safety of Vehicles (ESV) in Stuttgart, Germany.

The enhanced system is a pneumatically actuated reversible seatbelt pre-pretensioner. The belt pretensioning force comes from a compressed air motor and generates more than twice the tension forces provided by conventional electric pre-pretensioners.

Autoliv says the higher force significantly improves the performance especially in multiple impact collisions. During the first impact, which can be relatively soft and without an airbag deployment, the occupant is pulled back into an upright, safe position, thanks to the high force applied from the pneumatic pretensioner. With such a seatbelt system the occupant can be considerably better positioned for the second, more violent, impact when the airbag deploys for additional occupant protection.

Autoliv accident research data indicates that 25% of all accidents are of multiple impact nature. They result in a 3-times higher risk for significant injuries to vehicle occupants and a 4-times higher risk for fatal injuries.

Studies by Autoliv Research indicate that the average time-gap between the first and the second impact is approximately one second. Thanks to the higher force (300N) of the pneumatic system the pre- pretensioner needs only 0.36 seconds to pull the occupant back into a near upright position. The higher force will allow the seatbelt to pull back the occupant in 90% of the cases before a potential subsequent impact.

Interested participants can experience the performance of the pneumatic seatbelt pretensioner in a demo car at the ESV-conference. Two other pneumatically reversible safety functions are also shown in the demo-car: A hood lifter for pedestrian protection and a seatbelt buckle presenter which makes it easier to attach the belt when buckling up.