In the early 1970s, just as part of the ESV programme (Experimental Safety Vehicles), Mercedes-Benz built more than 30 test vehicles to research into future automobile safety systems. It is with these ESFs that the brand reflects its many years of systematic activities for the development of vehicle safety. They prepare the way for numerous innovations, some of which are only ready for series production years later. They include ABS, belt tensioners and belt force limiters, airbags, pedestrian protection measures and side impact protection.
In the 1960s one negative aspect of mass motorisation could no longer be ignored: more and more people were dying in road traffic accidents. In 1968, on the initiative of NATO, which was following the aim of addressing social challenges with civilian programmes at the time, the American Department of Transportation (DOT) started a programme for the development of Experimental Safety Vehicles (ESVs). In 1970 it called an international conference into being which has since 1991 carried the name Technical Conference on the Enhanced Safety of Vehicles.
Requirements for the ESFs: front and rear impact at 80 km/h
The first requirements for Experimental Safety Vehicles (ESVs) were defined in 1970. They included an extremely demanding front and rear impact against a rigid barrier at 80 km/h, and a side impact against a mast at 20 km/h. The test vehicles were also to withstand more minor accidents at 16 km/h without lasting deformation of the front and rear. It was believed that American consumers could not be expected to put on a seat belt by themselves. Automatic belt systems were therefore envisioned that would automatically wrap around the front occupants when the doors were closed.
The American government also issued an invitation to foreign countries to take part in this safety research. In 1970 this gave rise to the European Enhanced Vehicle Safety Committee (EEVC), which is still active today.
World innovation in 1959: safety body with crumple zones
Mercedes-Benz responded very positively to the challenge of designing safer vehicles. After all, the company could already look back on more than 20 years of continuous safety research at the time. In 1949, after the first beginnings at the end of the 1930s, the systematic research work resumed after the Second World War already led to the development of a safety door lock designed to prevent the doors from springing open in an accident. An improved version entered series production ten years later, in 1959 – together with the "unsharpened" interior designed to reduce secondary injuries. Also introduced was another world innovation that has saved many lives to this day: the safety body invented by Béla Barényi. Crumple zones at the front and rear absorb impact energy, with a rigid passenger cell between them. The safety body was the fundamental basis for all subsequent safety developments, and a pioneering milestone in vehicle safety.
In 1959 Mercedes-Benz also began systematic crash testing at the Sindelfingen plant, and this was to become an important part of the development process for new vehicle models. Ten years later the company intensified its safety development by forming the accident research department. This department analyses real accidents to systematically incorporate the findings into vehicle development (see separate section).
Project ESF: in four years Mercedes-Benz built 35 vehicles
From spring 1971 the ESF project in Sindelfingen went full speed ahead. More than 30 vehicles were built and tested over the next four years. The first test took place on 12 March 1971, with a series production car from the medium-class W 114 series: It took the form of a frontal impact against a fixed wall at 80 km/h. The crash tests also included front and rear impact tests, side impact tests against masts and other vehicles, and also drop tests from a height of 0.5 metres. As early as October 1971, Mercedes‑Benz presented the ESF 05 at the 2nd International ESV Conference in Sindelfingen.
However, the focus of the developers was not only on occupant protection in an accident based on correspondingly improved vehicle structures and new restraint systems. Even more than 40 years ago, Mercedes-Benz adopted its still continuing approach of comprehensive safety, as an extract from the description of the ESF 13 presented in May 1972 shows. It contains highly topical terms such as
- driver-fitness safety through seating comfort, climatisation and pleasant NVH (noise, vibration, harshness) characteristics.
- In the area of perceptive safety the ESF 13 included pneumatic headlamp beam control, headlamp wash/wipe function, monitoring of the rear lights from the interior, a rear window wiper and a safety paint finish using light colours and colour-contrasting strips.
- For exterior safety, i.e. the protection of pedestrians and cyclists, the ESF 13 featured e.g. front and rear bumpers with foam-clad side sections, rubber drainage channels and rounded door handles.
- Nor was fire safety neglected: The fuel tank above the rear axle was positioned well away from the exhaust system. A mechanism controlled by the oil pressure deactivated the fuel pump if pressure was lost. A valve system prevented a leakage of fuel if the vehicle was in an abnormal position. The materials used in the interior were flame-resistant, and a fire extinguisher was conveniently mounted on the front of the driver's seat.
All in all, Mercedes-Benz presented the following four ESFs to the public as part of the ESV programme:
ESF 5 Developed on the basis of the W 114 ("Stroke/8") series, presented at the 2nd International ESV Conference from 26 to 29 October 1971 in Sindelfingen
- Configured for impact speeds of up to 80 km/h
- Five three-point seat belts each with three force limiters, self-fitting front belts
- Driver and front passenger airbags, also an airbag in each front seat backrest for the outer rear passengers. Resulting increase in the weight of each front seat to 63 kilograms (standard: 16 kg).
- Extensive structural reinforcement of the front section and sides
- Kerb weight: 2060 kilograms (665 kg more than standard)
- Overall length 5340 millimetres (655 mm more than standard)
- Wheelbase 100 mm longer than standard to retain space in the rear despite larger seats
- Front section extension including hydraulic impact absorbers: 370 mm
- Experimental V6 engine to gain deformation space in the front
- Dashboard with metal impact absorber in the front passenger area
- Impact areas in the interior padded with polyurethane foam, especially doors, pillars and roof frame
- Power windows rather than window winders in the doors
- Headlamp wipers, beam control, parallel rear window wipers
- Side marker lights, rear lights with stationary relay and control system
- Windscreen and rear window of bonded laminated glass
- Pedals with rounded lower sections
- Anti-lock braking system (ABS).
ESF 13 Revised variant of the ESF 5, presented at the 3rd International ESV Conference from 30 May to 2 June 1972 in Washington (USA)
- Restraint systems and other details as in the ESF 5
- Kerb weight: 2100 kilograms (705 kg more than standard)
- Overall length 5235 millimetres (550 mm more than standard)
- Front section extension including hydraulic impact absorbers: 420 mm
- The changes in external dimensions were primarily the result of redesigning the front and rear ends. The bumpers could now be under-ridden, while the deformation path remained the same. The front and rear were extended to reduce the bumper overhang to a stylistically acceptable size.
ESF 22 Based on the S-Class (116 series), presented at the 4th International ESV Conference from 13 to 16 March 1973 in Kyoto (Japan)
- Configured for impact speeds of up to 65 km/h
- Four three-point belts, each with three force limiters and a belt tensioner
- Airbag instead of belt tensioner for the driver's seat
- Kerb weight: 2025 kilograms (287 kg more than standard)
- Overall length 5240 millimetres (280 mm more than standard)
- Front section extension including hydraulic impact absorbers: 245 mm
- Anti-lock braking system (ABS).
ESF 24 Modified S-Class (116 series), presented at the 5th International ESV Conference from 4 to 7 June 1974 in London (Great Britain)
- Restraint system as in ESF 22
- Kerb weight: 1930 kilograms (192 kg more than standard)
- Overall length 5225 millimetres (265 mm more than standard)
- Front section extension including hydraulic impact absorbers: 150 mm
- Anti-lock braking system (ABS).
All this provided an important basis for the safety level of car bearing the Mercedes star. The consolidated test report (1975) came to the same conclusion. It states: "The ESF 24 brings the project to a close, as this vehicle represents the best possible compromise between the original ESV requirements and our present production models."
Safety aspects having been part of the development process for new models as a matter of course at Mercedes-Benz for many years, the ideas first realised during the development of the ESFs entered series production in rapid succession. Milestones include the following:
- 1978: The anti-lock braking system ABS enters series production
- 1980: Introduction of the driver airbag and belt tensioner as a world innovation
- 1995: Belt force limiters and sidebags enter series production.
Mercedes-Benz also brought an immense number of other active and passive safety features to market, as the brand continues to be a pacemaker in the field of vehicle safety.
In keeping with this role, Mercedes-Benz presented a new Experimental Safety Vehicle in 2009. In presenting the ESF 2009, the brand not only marked two anniversaries, namely "50 years of the safety body" and "40 years of accident research", but also managed to bring the ESV Conference back to Stuttgart after 38 years. This ESF combined the latest concepts and ideas for further improvements in active and passive safety – with a time horizon that was often well into the future. Numerous innovations in the ESF 2009 have meanwhile entered series production.
ESF 2009 Developed on the basis of the S-Class (222 series), presented at the 21st International ESV Conference from 15 to 18 June 2009 in Stuttgart
- Beltbag – inflatable seat belt widening to lower the risk of injury, entered series production in 2013 in the S-Class (222 series)
- Braking Bag as an auxiliary brake in the vehicle's underbody, and possibly a new PRE-SAFE® component
- Child Protect – metal frame and padding for improved side impact protection, attractive appearance and "adjustment for growth"
- Hybrid Battery Shield – all-round electrical and mechanical protective measures for the lithium-ion battery, entered series production in 2009 in the S 400 HYBRID (221 series)
- Interactive Vehicle Communication – communication between vehicles. Initially an option in combination with the Drive Kit Plus in the A-Class in 2013, entered series production in the E‑C lass (213 series) in 2016.
- Interseat Protection – addresses the rare case when e.g. the driver and front passenger collide during a side impact. The interaction protection presented two different solutions: an airbag installed on the inner side of the driver's seat for the front occupants. In the second seat row the cushions could either be used as comfort features or activated as a PRE-SAFE® measure
- Partial high beam – LED headlamps with automatic light distribution adjustment and spotlight function to light up potential hazards, entered series production in 2017 as part of the combined MULTIBEAM LED and Night View Assist Plus system in the S-Class (222 series)
- PRE-SAFE® 360° – extended monitoring of the vehicle's surroundings up to 60 metres to the rear. As PRE-SAFE® PLUS, recognition of an impending rear-end collision was introduced in 2013 with the S‑Class (222 series) and the E-Class facelift (212 series). In this case measures are taken to warn following traffic and prepare the occupants for an impact.
- PRE-SAFE® Pulse – reduces loads acting on the upper body by preventively moving it towards the centre of the vehicle by up to 50 millimetres, entered series production in 2016 under the name PRE-SAFE® Impulse Side in the E-Class (213 series)
- PRE-SAFE® Structure – inflatable metal structures for additional stability of structural components
- Rear Seat Camera – rear seat monitoring for the driver
- Side Reflect – special reflective elements integrated into the door seals and tyres that are invisible by day make the vehicle's silhouette more clearly visible at night
- Size Adaptive Airbags – automatic adjustment of the front passenger airbag's volume to the seating position and stature of the front passenger detected by the sensors.
Every Experimental Safety Vehicle by Mercedes-Benz underlines the extremely broad technological horizon with which the brand continuously drives innovations in vehicle safety forward. Because all ESVs by Mercedes-Benz reflect measures designed to come closer to the vision of accident-free driving. The key aims on the way to this are
- to mitigate the severity of unavoidable accidents (e.g: emergency braking, active safety),
- to further improve passive safety while increasingly taking the pre-accident phase into account (PRE-SAFE®)
- and to put post-accident measures into place.