It's not just the strap across the chest - that existed before with the four and five-point belts used by racers and pilots. It was the addition of the mid-poi

It's not just the strap across the chest - that existed before with the four and five-point belts used by racers and pilots. It was the addition of the mid-point buckle that let the belt adjust to people of different sizes, plus the inertia reel in the B-pillar that made it acceptable to the consumer, and work as a safety device.