The newly developed electric motor with a range of more than 400 km, the pixel light peppered with 168 LED elements, the head-up display or natural speech recognition – the first electrified Astra is full of technical innovations. But the engineers have also further developed the compact class bestseller in less visible areas. One passive safety feature in particular now makes the Astra Electric even safer: the adaptive belt force limiter. It controls the belt force even more precisely, which acts on the body during a crash in order to reduce injuries as far as possible and at the same time to protect the occupants as best as possible.
The adaptively controlled restraint system uses sensors to recognize the severity of the accident, how tall and heavy the occupants are, and adjusts the belt force individually. A plus in safety that can make all the difference. Because despite all the airbags and assistance systems: “The seat belt is still the most important lifesaver in the car,” says Peter Schuessler, Manager from Rüsselsheim for passive restraint components. And the most important of all safety features is celebrating a round anniversary this summer: 50 years ago, after the factory holidays in 1973, Opel began to install standard three-point belt systems with practical one-hand operation in all models – and that at a time when seat belts were still three years away.
Opel was not only a role model at the time, the company actively campaigned for the acceptance of seat belts very early on. In 1969, Opel engineers demonstrated the results of their accident research program to representatives of the press in Dudenhofen. The most important message: more than half of all accident victims could still be alive if they had used seat belts. At the beginning of 1972, the management sent a letter to all Opel employees, asking them to wear their seat belts. There were discounted belts for retrofitting for all employees. The rush was huge, 12,000 copies were sold within a very short time.
irrational debate
It took time for the general public to accept the seat belt as an indispensable part of vehicle safety. Millions of people refused the lifesaver when, on January 1, 1976, seat belts became compulsory. Putting it on was considered too cumbersome for many. Especially when the car was used by different family members and the seat belt had to be adjusted in each case. A problem that the belt tensioner soon solved. For a long time, however, there seemed to be no cure for various prejudices: The seat belt curtailed personal freedom, and the safety effect was doubted. But the concerns quickly fell silent when the number of road deaths began to fall.
At the same time, the security specialists continuously improved the systems. In 1986, the Omega was the world’s first car to have height-adjustable seat belts in the front and rear seats – as standard. Airbags made their way into Opel models in the early 1990s. Since then, they have once again significantly reduced the risk of injury – under one condition: “You have to be buckled up: Seat belts and airbags only work optimally in combination,” explains Torsten Kerz, safety expert for occupant protection, “one holds back, the other cushions.” Together they absorb around two-thirds of the energy of an impact. The first belt force limiters were used from the 2000s to avoid peak loads. Other improvements increased comfort, such as the electric belt feeder in convertibles.
The smarter steering column gives way
Back in the 1960s, Opel engineers identified another key lever for more safety: the safety steering column. The fact that the steering wheel and pillar cannot penetrate the passenger compartment is still one of the starting points of the safety strategy. On the contrary: “In the event of an impact, the steering column contracts a little,” says Klaas Hillmann, the expert in the team for passive restraint system components. “In combination with the seat belt and airbag, we enable a dynamic absorber path of up to 100 mm.” Decisive millimeters that minimize the risk of injury.
A long history of success
With more than 20,000 victims, the number of road deaths in Germany reached a sad peak in 1970. Politicians reacted: The speed on country roads was limited to a maximum of 100 km/h, the blood alcohol limit was set at 0.8. However, the number only dropped significantly when seat belts were introduced in 1976, and in 1984 a fine was due for non-compliance. In 2020 there were fewer than 3,000 road deaths for the first time.
A lot has happened in 50 years: an average of 15 meters of seat belts are installed in every Opel model, which adds up to around 750 million meters of seat belt after five decades – that corresponds to 18 trips around the equator.
The adaptive belt force limiter now installed in the Opel Astra Electric has an even more refined “anti-lock braking system”. “The belt force is electronically controlled during the course of the crash,” explains Hoang-Thai Nguyen, a seat belt specialist. “In order to adjust the forces acting on the chest, four sensors are installed in the belt system.” In earlier versions, only single measurements were possible. This increase in awareness was made possible by the latest generation of crash test dummies, which have been in use since 2020.
Because of “dummies”
Because: The development of the safety belt is inextricably linked to the further development of the intelligent high-tech dummies, which simulate the effects of an impact on the human body in countless tests before a safety system is approved for series production. The latest generation goes by the name THOR. The abbreviation stands for “Test device for Human Occupant Restraint”.
Equipped with 200 sensors, THOR electronically senses and communicates what happens to him in a crash. With his help, the adaptive belt force limiter was developed, which is first used in the Mokka and now in the Astra Electric. It is another milestone in the decades-long development of passive safety features. And the possibilities are far from exhausted.
Older, younger, more diverse
From 2026, the next THOR generation will be able to simulate injury values that take the more fragile bone structure of seniors even better into account. From 2029 there should be a female THOR, a children’s THOR is also planned. “Of course, parameters such as size and gender are already included in crash tests – as in the past decades -” emphasizes Horst Müller, Manager for Seat Belts and Validation, “but the next THOR generation will take the findings to a new level.”
The Rüsselsheim team also has its sights firmly set on the future: Autonomous driving will turn a lot of things upside down again. Mainly due to the fact that vehicle occupants will no longer only sit facing forwards, but may face each other. And many will be chauffeured while lying down. For example, it is conceivable that the seat belts could be fully integrated into the seats. “We are already working intensively on the question of what that means in detail for the restraint systems,” explains Peter Schüßler. The success story of seat belts, which has been going on for five decades, is far from over.
Rüsselsheim pioneering role
The Opel Safety Vehicle 40 presented in 1974 was representative of the innovative strength of the Rüsselsheim company.
Safety has always had a particularly high priority at Opel. For example, the self-supporting all-steel body introduced with the Olympia in 1935 made it possible for the first time to construct targeted crumple zones and stable passenger compartments. The Opel engineers had already tested the belt intensively in the 1960s and decided to offer the restraint system as an option for some models. From April 1968, the Kadett, the Admiral and the Diplomat, among others, could be ordered with front seat belts. The classic coupé Manta A followed in October 1970. Opel also had the lifesaver as standard in the sporty models – for example in the Kadett B Rallye from 1967 and a year later in the Commodore A GS.
From the early 1970s, occupant protection became a particular focus. Evidence of this is the Opel OSV 40. The study presented in 1974 – based on a C-Kadett – was peppered with innovative safety features. The engineers filled the bumpers and all kinds of cavities in the interior and on the side of the vehicle with polyurethane foam. Four additional brake lights behind the rear window signaled emergency braking and served as hazard warning lights, while a two-part rear-view mirror minimized the blind spot.
Last but not least, the seat belts fitted to all four seats raised the feeling of security to a new level. The “Opel Security Vehicle” developed in the Dudenhofen test center performed above average in crash tests. After an impact at 65 km/h, all four doors could still be opened. Some innovations of the Opel OSV 40 made it into the series in a modified form, including the belt tensioners and the consistent further development of the crumple zone.
Seat belts became compulsory in 1976, accompanied by the “Click. First buckle up – then start.”
Photos: Opel