Remember when cars had just one airbag, in the steering wheel – or none at all? Those days are long behind us, as automakers fit airbags in every nook and cranny of their vehicles' interiors. So what's next?

Airbags on the outside of cars, that's what. Like this one, being developed by German supplier ZF (known principally for its transmissions). Billed as "the world's first pre-crash occupant safety system," it mounts an oversized airbag in the vehicle's rocker panel to act as a sort of inflatable crumple zone down the lower side of the car.

"Side impact collisions are among the most dangerous type of road traffic accidents," according to ZF, "accounting for nearly 700 deaths per year and nearly a third of all occupant fatalities on German roads."

To mitigate that figure, the system uses sensors mounted around the car to detect an imminent side collision and inflates a large airbag – between 280 and 400 liters, or 5-8 times the volume of a driver airbag – mere fractions of a second before impact: 150 milliseconds from when it detects the collision, or about the blink of an eye.

It's ostensibly similar to the hood-mounted airbags being developed by the likes of Volvo and Land Rover, but those are meant to protect the vehicle's occupants, not pedestrians. ZF says it could "reduce occupant injury severity by up to 40 percent."

The (silent) video above shows the system installed on a MkI Opel Insignia wagon, similar to the fifth-generation Buick Regal we got here in America (until its replacement two years ago). As it's still in the development phase, it might be a few years yet before the system will make its way to market on a car you can actually buy.