Beginning in May 1979, all new production cars in West Germany had to be equipped with front and rear safety belts, and effective August 1984, a mandatory use law applied to all seating positions.
In contrast to the front seats, where belt usage rates have exceeded 90 percent in the last few years, belt usage in the rear is only about 50 percent, in spite of iaws and punitive action by the government.
The poor acceptance of rear safety belts can be attributed to comfort and convenience factors, as well as the low perceived safety value. Belts with complicated fastening procedures frequently remain unused, while belts that are uncomfortable are soon unfastened. Some belts remain unused because occupants doubt the ability of a belt to be quickly released after an accident.
BMW decided to develop a new rear safety belt system that would overcome most of these problems. The result is a belt whose most significant new design characteristic is a reversed shoulder belt geometry - the upper mounting points are inboard and the diagonal shoulder belt angle across the torso is in a direction opposite to what is customary. This enables placement of the female half of the buckle on the outboard side, integrated into the seat and well forward for easy access. Buckling these belts is a one-hand operation that is as quick and simple as putting on a front safety belt. After opening the rear door, people are ‘invited’ to put the belts on.
The forward location of the outboard buckle also makes pelvic restraint more effective in head-on collisions, reducing the likelihood of submarining and abdominal injury.