How
In the event of a front or side impact above a certain limit where the SRS is deployed, the pretensioner instantly rewinds part of the seatbelt webbing to maximise the restraining effect on the user. If the load on the seatbelt increases due to the forward movement of the user's chest, the load limiter pays out a small amount of the seatbelt while maintaining a restraining effect. This operation reduces the pressure applied to the user's chest - reducing the risk of injury.
With SRS the pretensioner will always operate in unison with the airbags. With i-SRS the pretensioner is independent. In a moderate accident where airbags will be of no assistance only the pretensioners may be activated.
In the event of a front or side impact…, the pretensioner instantly rewinds part of the seatbelt webbing to maximise the restraining effect on the occupant