Restraint and assistance systems

  • Seat belts in all Mercedes-Benz passenger cars from 1958
  • Airbag debut in the S-Class in 1981
  • Safer motoring with electronic aids:  ABS & Co.
180 Db saloon from 1959

180 Db saloon from 1959

After the introduction of the safety passenger cell with crumple zones at front and rear and the reduction of potential sources of injury within the passenger compartment by the use of padding and new materials, efforts to achieve a high level of crashworthiness were predominantly directed at restraint systems in the 1970s. Safety developments that were started in the era of the ESV project, such as belt tensioners and airbags, were perfected and incorporated in production vehicles. The basis for the development of restraint systems was the introduction of the seat belt as an equipment option. This was announced in 1957, starting with the Mercedes-Benz 300 SL roadster.

Fasten your seat belts, please

In 1958 – just one year later – seat belts were available for all Mercedes-Benz passenger cars equipped with individual front seats. The first seat belt versions were lap belts. Federal German Chancellor Konrad Adenauer was one of the customers to opt for these early dual-anchorage seat belts. A lap belt was installed for him in the rear of his Mercedes-Benz 300. From 1961 onward, Mercedes-Benz exclusively offered dual-anchorage shoulder belts for individual seats.

Lap belts on the front seats became optionally available as early as 1957

Standard seat belt anchor points facilitated retrofitting and were introduced for front seats in November 1961, for rear seats in 1962. In 1966, the simple belts stretching from shoulder to seat that had been the norm until then were replaced by three-point seat belts. Until the introduction of the three-point inertia-reel seat belt as standard equipment on the front seats in 1973, the seat belt remained an optional item of equipment. With the installation of seat belts as standard equipment, Mercedes-Benz was acting in advance of the law obliging motor manufacturers to install front seat belts as standard as of January 1, 1974. Two years later, on January 1, 1976, drivers were obliged by law to wear a seat belt while driving. To begin with there was no penalty for failure to wear the belt, which may seem peculiar from the modern perspective. But in those days the seat belt was a highly contentious issue. Not until 1984 was a fine of 40 DM introduced for driving without use of a seat belt.

World safety premiere:  Airbag in the S-Class (W 126 series)

Mercedes-Benz Type 500 SEL, (W 126)

Type 500 SEL Saloon

In 1981, at the International Geneva Motor Show, Mercedes-Benz presented a sensational passive safety innovation in an S-Class car from the W 126 series: the airbag. As of summer 1981, the protective airbag was optionally available for the top-of-the-line model of Mercedes-Benz. Together with the seat belt, which by then was combined with an innovative belt tensioner in the S-Class, the airbag protects the driver in an accident by cushioning the impact against the steering wheel. To achieve this, a sensor triggers an explosive charge within just 40 milliseconds of an accident occurring, thus inflating the protective air cushion in such a precisely controlled manner as to achieve maximum protective effect when the upper body comes into contact with the airbag. The airbag is regarded as an additional safety system (Supplementary Restraint System, SRS) and complements the effect of the seat belt.

Airbag in the steering wheel

After its world premiere in an S-Class sedan, the driver airbag soon gained company when Mercedes-Benz introduced the front passenger airbag in 1988. In 1992, the driver airbag became standard equipment in all Mercedes-Benz models, followed by the front passenger airbag in 1994. One year later, the developers of the Stuttgart-based company presented the side airbag in the E-Class, which opens across the doors in just 20 milliseconds after a collision. Recent developments in airbag technology include adaptive systems which adjust to the severity of an accident.

Mercedes-Benz diagram from 1980 explained how the airbag and belt tensioner worked

Mercedes-Benz diagram from 1980 explained how the airbag and belt tensioner worked

With the introduction of the airbag in 1981, Mercedes-Benz once again wrote safety history. Accident research has proven the importance of this restraint system for vehicle occupants in the event of a crash. Airbags have saved lives in thousands of accidents. Today, more than twelve million Mercedes-Benz vehicles are equipped with airbags. The belt tensioner, which was presented at the same time as the airbag, has also secured its place as an element of passive safety. From 1984 onward, all Mercedes-Benz models have been equipped with belt tensioners as standard on the front seats. In 1995, the belt tensioners of all models were combined with belt force limiters which adapt the performance of the restraint system to individual requirements.

Anti-lock Brake System ABS

Test cars with and without ABS brakes

Test cars with and without ABS brakes

In the 1970s, Mercedes-Benz did not just put great effort into researching passive safety; much research was also performed on active safety technology. An outstanding result of this work was the world premiere of the anti-lock brake system (ABS) in the S-Class (W 116 series) in 1978. ABS is a landmark innovation and assistance system which ensures that a vehicle remains steerable even in the event of emergency braking. Mercedes-Benz developed the system together with Bosch and has been installing ABS as standard equipment in all Mercedes-Benz models since 1992.

S-Class sedans from the 116 series with and without anti-lock braking system (ABS) on the test track in Untertürkheim, 1978

In the event of emergency braking or brake application on slippery ground, there is always a risk that the wheels may lock up and cease to provide lateral stability, causing the unsteerable vehicle to skid. To prevent wheel lockup, ABS uses wheel speed sensors to measure the behaviour of each individual wheel during deceleration and regulates the brake pressure applied by the driver at each wheel so that even in the event of emergency braking on slippery ground, the wheels do not lock up. The automobile thus remains steerable and retains its directional stability even under critical circumstances – within the limits of what is physically possible, of course. The driver is informed of ABS intervention by the pulsing of the brake pedal or by the flashing of the triangular yellow ABS/ESP® indicator lamp.

Assistance systems for active safetyMercedes-Benz. Basic function of ESP in the event of oversteer.

In the 1990s, Mercedes-Benz introduced a whole range of assistance systems which improved the active safety of its models. The Electronic Stability Program (ESP®) which was first presented in 1995 in an S 600 Coupé from the 140 series, initiates selective brake actuation at individual wheels in critical driving situations and also adapts the engine output so that the vehicle can be stabilized. ESP® is of particular benefit in bends and during sudden evasive manoeuvres. The system recognises critical situations, for example, by using the yaw velocity sensor to monitor any sudden rotational or skidding movements of the vehicle or detect wheel spin. Depending on situation and requirements, ESP® restores stability by selectively braking one or more wheels. In addition, engine torque is reduced if required. All Mercedes-Benz passenger cars have been equipped with ESP®since 1999. Other assistance systems such as Brake Assist (BAS, introduced in 1996) and Active Body Control (ABC, introduced in 1999) improve the active safety of Mercedes-Benz vehicles still further.Mercedes-Benz. Basic function of ESP in the event of understeer.

With BAS, Mercedes-Benz is the world’s first motor manufacturer to actively enhance driving safety and brake power in critical situations. Brake Assist is today installed in all Mercedes-Benz passenger cars as standard and interprets the braking behaviour of the driver. When an emergency braking situation is detected, it builds up the full brake power available if the driver steps on the brake pedal quickly, but too hesitantly. The assistance system thus compensates for insufficient pressure on the brake pedal in dangerous situations and enables a shorter braking distance.

Brake Assist System (BAS)

This significantly reduces the seriousness of any impact for all parties involved in the accident. This development is based on a finding of the Mercedes-Benz Accident Research department, namely that car drivers step on the brake pedal quickly in critical situations but do not apply enough force. Tests have provided impressive documentation of the effectiveness of this assistance system. On a dry road surface, most drivers require up to 73 meters of stopping distance when performing emergency braking from a speed of 100 km/h. However, with BAS, the vehicle comes to a standstill after just 40 meters; this corresponds to a reduction in stopping distance of approx. 45 percent. Brake Assist has been standard equipment since December 1996, initially in the S-Class and SL-Class. Today, every Mercedes-Benz is equipped with Brake Assist.

Active Body Control, S-class coupé (no ABC), CL-class (with ABC)

Active Body Control (ABC), the active suspension and damping system, automatically adapts the suspension setting to the respective driving situation. The sprung mass vibrations of the vehicle are reduced and optimally dampened according to requirements when the vehicle is starting off, cornering and braking. A high-pressure hydraulic system, a high-speed computer and a sophisticated sensor system ensure that the bodywork remains stable in all driving situations. ABC almost completely suppresses both the pitching that otherwise occurs when starting off and braking and the rolling motion that occurs during cornering.

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