From 1950, when officials began tracking traffic accidents, to 1970, the number of fatalities in Germany rose from 7,408 to 21,332. Similar increases were recorded in other European countries and the United States. The dramatic increase in deaths was the result of higher average speeds, a rapid increase in traffic density, and inadequate vehicle safety systems. In the event of a crash, passengers were hurled from their vehicles, were badly bruised, or were injured by the hard, sharp, and pointed sections of the cars’ interiors.

As a result, traffic experts began to call for safety systems. One area of research examined the strengthening of the passenger compartment and the construction of “deformation zones” that absorb the impact energy of a crash. Another area of research explored restraint systems that would keep passengers in their seats and thus prevent them from being seriously injured.

The first restraint system to be incorporated into vehicles was the seatbelt. This protection system took effect when European countries began to impose seatbelt laws in the middle of the 1970’s – Germany’s version took effect on January 1, 1976. The mandatory use of seatbelts led to a drastic decrease in traffic fatalities. One alternative to the seatbelt was so-called passive restraint systems that did not require the passenger to buckle up.

In their research, experts realized that the airbag, a device that would pop out of the steering wheel’s impact absorber and inflate with lightning speed, had a tremendous future as a passive restraint system. Once inflated, the airbag would keep the passenger in his seat upon impact and prevent him from being injured. The first airbags – patented by the Americans A.H. Parrot and H. Round in 1920–were permanently inflated pillows designed to protect airplane passengers during crashes. The first patents for airbags that would inflate upon impact were issued to the American John Hetrick and the
German Walter Lindner in 1952 and 1953. It took about 15 more years before the first efforts to design airbags for passenger cars were made by the automobile industry in 1969.

During the research into passive restraint systems, Robert
Bosch GmbH focused on the management of the airbag
activation and the simultaneous activation of the seatbelt
pretensioner. Beginning in 1977, Bosch researchers worked with automakers on the system. In cooperation with the auto industry, the company tested triggering devices in 6,200 crash simulations conducted with 60 vehicle models of 15 different makes. The control system was used for the first time in the Mercedes-Benz S-Class in December 1980. To effectively protect a vehicle’s passengers, the electronic system had to have a reaction time of 10 milliseconds from impact to activation of the airbag.

The basis of the system is an acceleration sensor. Based on a measurement of the deceleration curve, the evaluation circuit can determine whether the driver has hit the brakes, bumped into a parked car, or jumped over the curb, or whether the vehicle is involved in a serious accident that could endanger the travelers’ lives. Within 10 milliseconds the pyrotechnical gas inflator has to be ignited in order to protect the driver. An additional 30 milliseconds later, the airbag will be fully inflated and effective. This is just enough time to keep the driver from being thrown against the dashboard – which would take only 40 milliseconds during a frontal collision at 50 kilometers an hour.

Today, these electronic helpers control up to 20 passenger restraint systems – from the airbag for the driver and passenger to the side and head airbag and the seatbelt pretensioner.

Crash test with the airbag
When a vehicle is traveling at 50 kilometers per hour, a total of 50 milliseconds expire from the first picture until the last picture.