Audi's Procon-Ten safety system

An Audi UK promotional video for Procon-Ten, made in 1990.

In the second half of the 1980s, airbags were appearing on increasing numbers of cars. However, airbags were expensive, involved a large, aggressively inflating bag in close proximity to occupants, and had the potential to not inflate when they could be of benefit. 

Enter Audi's "procon-ten" (programmed contraction/tension) system, first introduced in 1986. All Audi engines of the era were longitudinally mounted, which means the longest axis of the engine is parallel to the longest axis of the car. This meant that the front end of the engine was only a few inches from the front bumper, so if the car had a frontal impact, the engine would get struck early in the crash. 

Audi used this to their advantage, wrapping stainless steel cables around the engine block and connecting them to the seat belts and steering column. As soon as the engine was struck, the cables would tighten the seat belts and pull the steering wheel out of the way, both holding occupants tighter to their seats and giving the driver more room to slow down. 

Procon-Ten was an effective system; while limited crash-test data is available, a 1989 Audi 80 with the system did well in a 35 mph (56 kph) full-frontal crash test conducted by NHTSA, and a 1991 Audi 100 did well in a 34 mph (55 kph) offset crash test. 

Procon-Ten was discontinued after the 1994 model year.