Method for triggering a motorized retractor for a safety belt system of a vehicle with the setps of - detecting a low friction road condition (LowMu) when an ABS-sensor generates a signal and a longitudinal deceleration sensor senses a deceleration (Ax) which is lower than a predetermined value, or a brake pressure sensor detects a brake pressure, which exceeds a predetermined value and a longitudinal deceleration sensor senses a deceleration (Ax) which is lower than a predetermined value, and - triggering the motorized retractor when the low friction road condition (LowMu) is detected and the brake pressure sensed by a brake pressure sensor exceeds or falls below one out of three predetermined thresholds (Th1, Th2, Th3) to apply one out of three different restraining forces (L1, L2, L3) in the safety belt system, and - the motorized retractor is triggered to apply a first level of the restraining force when the brake pressure sensor senses a brake pressure which exceeds a first threshold for a predetermined first time interval, and - the motorized retractor is triggered to apply a second level of the restraining force, which is higher than the first level of the restraining force when the sensed brake pressure is not falling below a second threshold within a predetermined second time interval while the first level of the restraining force is applied and wherein - the second threshold is lower than the first threshold of the brake pressure, and - the motorized retractor is triggered to apply a third level of the restraining force when a brake pressure is sensed which exceeds a third threshold and wherein - the third level is higher than the first level and the second level and the third threshold is higher than the first threshold and the second threshold. - detecting a low friction road condition (LowMu) when an ABS-sensor generates a signal and a longitudinal deceleration sensor senses a deceleration (Ax) which is lower than a predetermined value, or a brake pressure sensor detects a brake pressure, which exceeds a predetermined value and a longitudinal deceleration sensor senses a deceleration (Ax) which is lower than a predetermined value, and - triggering the motorized retractor when the low friction road condition (LowMu) is detected and the brake pressure sensed by a brake pressure sensor exceeds or falls below one out of three predetermined thresholds (Th1, Th2, Th3) to apply one out of three different restraining forces (L1, L2, L3) in the safety belt system, and - the motorized retractor is triggered to apply a first level of the restraining force when the brake pressure sensor senses a brake pressure which exceeds a first threshold for a predetermined first time interval, and - the motorized retractor is triggered to apply a second level of the restraining force, which is higher than the first level of the restraining force when the sensed brake pressure is not falling below a second threshold within a predetermined second time interval while the first level of the restraining force is applied and wherein - the second threshold is lower than the first threshold of the brake pressure, and - the motorized retractor is triggered to apply a third level of the restraining force when a brake pressure is sensed which exceeds a third threshold and wherein - the third level is higher than the first level and the second level and the third threshold is higher than the first threshold and the second threshold.