A vehicle seatbelt apparatus includes a seatbelt web wrapped in a reel around a motor-rotated shaft. A latch is selectively engageable with the reel to lock a seatbelt retractor from movement in one direction while allowing movement of the retractor under motor rotation of the shaft in response to pre-crash vehicle braking deceleration, a vehicle downhill angle or a vehicle lateral g force exceeding a threshold. When a retractor locked position is detected, the motor is activated to retract the seatbelt web for a predetermined time period to urge the passenger toward a center upright position in a vehicle seat.

A modular system (11) for a belt tensioner (10) comprising a spur gearing (18) comprises plural step wheel pairings of a first step wheel (28) and a second step wheel (30), wherein for each of the step wheel pairings the number of teeth of the first step wheel (28) and the number of teeth of the second step wheel (30) are different from those of the other step wheel pairings, but the distance between a shaft (44) of the first step wheel (28) and the shaft (44) of the second step wheel is equal for each of the step wheel pairings. In addition, the modular system (11) comprises identically designed housings (20) into each of which a spur gearing (18) with one of the step wheel pairings can be introduced.