Procon-ten was a notable safety feature comprising a series of hidden steel cables routed behind the gearbox, attached to the steering wheel and front seatbelt inertia reels. In the event of a front impact, the engine and gearbox are forced rearwards, pulling on these cables. This action simultaneously pulls the steering wheel into the dashboard to prevent the driver colliding with it while tightening the front seatbelts. This innovation was a precursor to the airbag, which became popular on mass produced cars during the 1990s after being patented by Mercedes-Benz in 1982.