The present disclosure relates to a method for controlling a time of activation of a restraint system in a vehicle, the vehicle comprising a seat belt associated to a seat, the restraint system being a reversible restraint system, the method comprising the steps of a) determining a current length (L) of pulled out seat belt, b) detecting a collision or an imminent collision involving the vehicle, c) predicting a time (T0) when the collision is predicted to affect a user of the seat belt, d) activating the reversible restraint system a selectable time period (Δ1) before the time (T0) when the collision is predicted to affect the user of the seat belt, wherein a length of the selectable time period (Δ1) is a function of the determined current length (L) of pulled out seat belt. The disclosure further relates to a safety arrangement of a vehicle.