COLOGNE: There's the squeal of tyres, the crash of breaking glass, and then the airbag immediately inflates. The now ubiquitous safety device that protects the head and upper body in a car crash first made its appearance in vehicles half a century ago.
This is how it works: sensors register a collision and trigger a propellant charge that causes a textile bag to instantly inflate with compressed air, cushioning the head.
Together with the three-point safety belt it's played a crucial role in reducing deaths and injuries in collisions.
The origin of the air bag goes back a long way. In 1951 Walter Linderer patented the idea for an “inflatable container in a folded state that inflates automatically in the event of danger.”
However, it wasn't until the 1970s that the device began to make its way into cars. The high number of accidents in the US led to laws demanding more protection for the occupants of cars.
One response from General Motors was the Air Cushion Restraint System (ACRS). From 1974 onwards, GM offered an airbag for drivers and front passengers in some of its models at an extra cost.
GM's airbag was initially aimed at replacing the three-point seat belt that some drivers found uncomfortable, according to motoring journalist Wolfgang Blaube: "Only a lap belt and knee pads were part of the system."
The GM airbag disappeared from production after just two years. “The maintenance was very time-consuming and expensive,” says Blaube. "Quite a few owners had the system deactivated over time and three-point belts installed."
Things changed when Daimler-Benz offered an airbag as a supplement to the three-point seat belt, a principle that still applies today.
In 1971 the German car maker patented a technical solution aimed at being an "impact protection device for the occupant of a motor vehicle."
One of the toughest problems to solve was how to inflate the airbag in just 30 milliseconds.
"The breakthrough in the rapid generation of gas came with solid propellant, as used in rocket drives," says Professor Rodolfo Schoeneburg from Mercedes-Benz.
Another challenge was that the driver's airbag had to be safely housed inside the steering wheel while the sensors had to be able to differentiate between an accident and a minor parking bump.
Daimler-Benz debuted the airbag as an optional extra in the Mercedes S-Class sedan in 1981, along with a seat belt tensioner that pulled the belt tight in the event of an accident.
The car maker called this SRS (Supplemental Restraint System) and it worked in conjunction with the airbag to reduce injury.
Today airbags have long been standard. They're much smaller than they were originally and can be found in many parts of the car, not just the steering wheel.
Professor Schoeneburg believes they'll be around for a few years yet, despite advances in car safety such as driver assistance systems.
Professor Lutz Eckstein, director of the Institute for Motor Vehicles (ika) at RWTH Aachen University in Germany, also considers that airbags and restraint systems will continue to be important in the future.
"We are currently on the threshold of automated driving and must therefore further develop occupant protection," he says.
Robot cars will mean that a human doesn't have to sit at the wheel anymore and could be lying or sitting in different postures.
That will require precisely determining the exact posture of the passengers using sensors and thermal imaging cameras, and then aligning airbags to be in the right place if there's an accident.
In addition, "there are still deficits for the outside area, to provide protection for other road users such as cyclists or pedestrians. There is still development potential," Eckstein says.
