Safety First
Commitment to automotive safety at Mercedes-Benz spans generations
Article Gary Anderson
Images Daimler Archives, Daimler Global Media
The developers of Mercedes-Benz automobiles have had a commitment to making the safest possible vehicles for as long as the company and its predecessors have been building automobiles. One of the first modifications Bertha Benz made to the Patentwagen on the historic first automobile journey was to add leather pads to the brake pressure plates to improve the stopping capability of her three-wheeled machine.
At the media TecDay in Stuttgart earlier this year, safety engineers reviewed the history of innovations in safety systems pioneered by Mercedes-Benz. As the design of the automobile has evolved, improvements that reduce the frequency and severity of accidents can be roughly divided chronologically into three eras.
The first advances were generally passive, built into the vehicle’s structure and components, so that if the driver was unable to maintain control or it collided with another vehicle or obstacle, the extent of damage and injury was mitigated.
More recently, Mercedes-Benz engineers have designed active systems that change the dynamics of the vehicle’s operation to help the driver avoid unsafe situations and respond more effectively to those situations as they occurred.
Overlapping the first and second eras, focused analysis of real-world accident data at Mercedes-Benz and the sharing of development information with other manufacturers under the auspices of international government organizations increased the pace of safety-systems development worldwide.
Today, and into the foreseeable future, engineers are designing interactive safety systems in which the automobile senses external conditions and other vehicles on the road, then communicates with them and reacts itself to avoid collisions without intervention by the driver.
Passive safety systems
Mercedes-Benz was among the earliest automobile companies to recognize that it had a responsibility to design its vehicles in such a way that collisions would be less likely and passenger injuries less serious.
The initial focus was to improve the structural rigidity of the automobile so that passengers were more likely to survive a collision or rollover. This was a major advantage of the unibody chassis that Mercedes-Benz adopted in the early 1950s. With stress forces spread across the vehicle’s entire body, rather than acting on the separate components of a body-on-frame assembly, the integrity of the passenger cell could be maintained.
The 300SL was an extreme example of this ethos: despite its famous gullwing doors, the 300SL could survive a rollover without the top collapsing, and the doors were designed to be opened even if the vehicle landed upside down. To prevent doors from bursting open in collisions or rollovers, the company patented the “conical-pin” safety door lock in 1949.
After World War II, the goal of reducing the extent and severity of automobile accidents accelerated under design engineer Béla Barényi, building on technology developed during that conflict. By 1951, Barényi had patented a “safety body” that protected a rigid passenger compartment using crumple zones – structural areas that would collapse in a predictable manner and absorb the energy of the impact – around the passenger compartment.
In another advance, Mercedes-Benz was the first company to introduce crash and rollover testing of its vehicles as part of new-model engineering and development. Rudimentary crash dummies, another innovation, added to the information gained from this testing. Benefits of new designs were no longer theoretical; they were tested and improved before introduction.
While the new collapsible structural system was being refined and designed into models under development, Mercedes-Benz signaled its commitment to safety by upgrading small components, such as the energy-absorbing steering wheel in 1954 and spring-mounted star hood ornament in 1957 (see Artifact, page 6), the first to offer the driver some protection in accidents and the second to protect pedestrians in the event of a collision.
By 1959, the crumple-zone body design had been tested and introduced in the all-new W111 designs. Henceforth, it would be integrated into every new model as it entered production.
Efforts to reduce the extent of injury in accidents continued. By 1967, the concept of an energy-absorbing steering wheel had been extended to the design of a collapsible steering column, which would retract on impact from the driver. Throughout this period, Mercedes-Benz worked in cooperation with other manufacturers to increase acceptance and improve the effectiveness of seat-belt systems to hold drivers and passengers in place, focusing on belt design and anchoring systems.
By 1981, recognizing that belts were not sufficient to limit injuries, attention had moved on to use of air bags, beginning with a steering-wheel-mounted bag, then progressing to a front- passenger bag, resulting in today’s comprehensive air-bag systems throughout contemporary vehicles.
With vehicle crash-testing now a mandated requirement for all manufacturers, and with increased knowledge of metal alloy attributes, Mercedes-Benz continues to improve the structural design of chassis – including both new crumple zone designs and variable-strength metal alloys – to allow different structures to collapse at different rates and under different forces.
Organized safety-system research
Starting in 1969, the firm began investigating all accidents within 200 kilometers of Stuttgart involving Mercedes-Benz vehicles – 4,800 accidents so far – to create a collision database.
At the same time, governments of the United States and European countries were becoming concerned about the increasing numbers of traffic deaths and the possibility that changes to automobile design might mitigate this problem.
In 1968, the American Department of Transportation (DOT) started a program for the development of Experimental Safety Vehicles (ESVs), responding to the NATO initiative that aimed to address social challenges, like traffic safety, with civilian programs. As an industry leader, Mercedes-Benz has been a key player in this effort from the very beginning.
Active safety systems
By the early 1960s, a parallel program of safety research and development had begun, focusing not just on limiting injuries and death in collisions and loss of control, but also on helping the driver avoid the accident in the first place.
Automotive brakes, regarded as the key mechanical element available to avoid collisions, were the first focus. Introducing an innovative dual-circuit braking system as standard equipment on all models by 1963, the company assured that a failure in one part of the system wouldn’t result in complete loss of brakes.
In 1953, Mercedes-Benz had patented a system that would prevent the wheels from locking under braking by sensing variations in the speed of individual wheels and pulsing the brakes to maximize traction and avoid potential loss of control under panic braking and slippery pavement conditions.
The major conceptual breakthrough in the development of the antilock braking system (ABS) was integration of electronic vehicle sensing and actuation controls with the direct hydraulic controls operated by the driver, ushering in a new era of active safety systems in which the vehicle assisted the driver to maintain control and avoid accidents.
By 1963, practical development of ABS had begun and in 1966, Mercedes-Benz began working with a company – eventually merged into OEM supplier Bosch – to develop a practical system for production. Recognizing the benefits of ABS, Daimler-Benz decided to share safety advances with other manufacturers and invited them to participate in development of future systems.
The ABS system was introduced as an option on the W116 model in 1978, the first production car to offer ABS commercially. By 1987, ABS was standard on all automobiles produced by Mercedes-Benz. With ABS in operation, not only was it possible to bring a car to a stop without skidding, it was also possible to maintain steering control with the brakes engaged. Today, ABS in cars is a matter of course for virtually every manufacturer worldwide – thanks to the innovative culture at Mercedes-Benz.
With the benefits to be derived from computer-control systems monitoring sensors throughout a vehicle and directing electronically activated components in response, wiring systems rapidly became too complex for traditional wiring harnesses. Mercedes-Benz was among the first manufacturers to introduce an enabling technology – Controller Area Network wiring systems linking sensors and actuators to the Electronic Control Unit (ECU) computer processor while using message- control technology to run many different signals along the same wiring at the same time – that dramatically reduced the complexity and weight of the wiring harness and allowed more and more sensing-processing-actuation systems to be added to the automobile.
The data supplied by the ABS sensors could also be used by other assistance systems such as anti-slip control (ASR) and the automatic locking differential (ASD) – available beginning in 1986. The newly developed 4Matic traction system, a fast engaging and disengaging four-wheel-drive system, premiered in 1985. Mercedes-Benz introduced a newly designed 4Matic system in the E-Class model series 210 in 1997.
With sensors and actuators connected to ECUs, the next major step was to address potential loss of control in extreme handling situations. The Electronic Stability Program (ESP), jointly developed by Daimler-Benz and Bosch, premiered in Mercedes-Benz S-Class series 140 in March 1995. It assisted the driver by applying a specific braking force on one or more wheels and – if necessary – by adjusting engine torque. It used a far more extensive sensor system than ABS and ASR, including steering angle, lateral acceleration and yaw-rate sensors, which allowed detection of skidding movements. The ESP became the worldwide standard in 1998. In 1999, Mercedes-Benz became the world’s first brand to equip all its passenger-car models with ESP as standard.
The advance of driver-assistance systems has continued. Adaptive headlights now turn with steering input and automatically dim or change their projection field to avoid distracting oncoming drivers. The night-vision camera and display system, with pattern recognition of pedestrians and alerts to the driver, was launched as an option in 2009, and 360-degree vision using a combined image from four external cameras became available in 2011, reducing the chance of running over an obstacle or child playing out of the driver’s direct field of vision.
Interactive safety systems
During the early 1990s, with improvements in computing, artificial intelligence and sensing, vehicle safety entered a new age as the idea of cars driving themselves began to move from science fiction to science fact. The basic premise was that the vehicle itself would have the capability to sense external conditions, evaluate the implications and respond in an intelligent manner. Though fully autonomous vehicles are still some years in the future, the near-term benefit was the development of interactive safety systems that could anticipate and respond to changing conditions that could lead to accidents.
The first such system was Parktronic with Active Parking assist, initially demonstrated on production models in 1995. Sensors on the front, back and sides of the vehicle measured distance to the curb and to cars ahead and behind; a computer algorithm controlled the steering, power and braking so that the vehicle could park itself without human intervention.
By 1998, radar capable of measuring the distance to cars ahead was practical and inexpensive enough to be added to a vehicle, and Mercedes-Benz introduced Distronic Plus cruise control; when enabled, the system allowed the car to adjust speed to maintain a safe stopping distance in traffic. Journalists were initially skeptical of the concept, but over the past 20 years, active cruise control has become a desirable feature available to the public on an increasing number of models at lower and lower price points.
As Distronic Plus began to make people grow comfortable with the idea that their automobile might take action in advance of their own awareness of a change in conditions – slowing down as the traffic ahead bunched up while the driver was distracted by changing a CD – other devices began to be conceptualized, then added.
The next big advance was in sensing as autonomous- driving research improved both vision and pattern recognition capabilities. This research into methods of having a car drive itself in urban-traffic situations precipitated the addition of a dual camera behind the rear-view mirror and a rear-facing camera; improved computer ability to recognize lane lines and pedestrians ahead of the car and enhanced steering and braking intervention. As a result, in just the last five years, Mercedes-Benz has been able to add Active Lane-Keeping Assist, front anti-collision protection, Pre-Safe anticipatory occupant protection with rear and cross-traffic pedestrian and car warning and collision mitigation.
The majority of the company’s sophisticated new safety systems introduced under the rubric of Intelligent Drive are still optional on most current Mercedes-Benz automobiles. Nevertheless, sales data indicates customers are increasingly choosing the safety-equipment packages and more packages are becomiing standard. Meanwhile, the ongoing reductions in rear, side and front collisions are measurable and significant. Mercedes-Benz’s stated goal of building a collision-proof automobile is now actually starting to seem achievable.
SIDEBAR
Experimental Vehicles and Safety Forums – 1959-2019
W111 Test Vehicle – 1959
Predating dedicated experimental safety vehicles at Mercedes-Benz were legions of test mules, such as this W111, used during development of the world’s first automobile with a safety body, built with a stiff cabin structure and energy-absorbing crumple zones front and back.
ES3 & ES5 – 1971
Under the auspices of the North Atlantic Treaty Organization, the U.S. Department of Transportation organized the first international conference on vehicle safety in 1970, inviting European manufacturers, including Mercedes-Benz. The company began building experimental safety vehicles, each incorporating a host of safety advances to test their effectiveness and interaction with one another. With the first conference focused on creating standards for front and rear collision protection, Mercedes-Benz built a series of safety cars to focus on structural improvements and crash-testing for the October 1971 conference. Two of these cars, ES3 and ES5, were displayed at the conference, held at the Mercedes-Benz safety research facilities in Sindelfingen. Built on the medium-sized W114 chassis, these vehicles were able to withstand front and rear impacts against a fixed wall at 50 mph, side impact against a post, and a drop test of 0.5 meter, without impinging on the passenger cell.
ESF13 – 1972
Following the 1971 conference, Mercedes-Benz engineers expanded the firm’s safety efforts. ESF 13, a refined variant of ESF5 on the same W114 chassis, was presented at the conference in June 1972. Innovations included better driver comfort with upgraded seating, climate control and reduced noise, vibration and harshness. Enhanced exterior safety and stronger headlights better protected pedestrians and cyclists while changes in fuel-tank position and valving reduced the chance of fire in accidents
ESF22 – 1973
Built on the new W116 S-Class, ESF22 was displayed at the fourth International Safety Vehicle conference in Kyoto in March 1973. Key additions included the anti-lock braking system, and steering-wheel airbag. Hydraulic shock absorbers behind the front bumper increased to 40 miles per hour the collision speeds that could be absorbed without passenger compartment impingement.
ESF 24 – 1974
At the June 1974 conference in London, an enhanced version of the prototype safety vehicle built on the same W116 S-Class chassis was unveiled. This vehicle basically improved the systems of the ESF 22, with the same benefits but with shorter hydraulic impact absorbers, reduced vehicle length and weight, and improved ABS operation.
ESF2009 – (W222 S-Class)
Having achieved the goals set out at the first international conference in 1970, Mercedes-Benz now continued to work on all aspects of safety, focusing on the development and introduction of active safety systems. By 2009, progress in this area was significant, warranting the construction of another prototype safety vehicle. At the 21st International ESV conference, held in Stuttgart, June 2009, Mercedes-Benz introduced ESF2009. This new vehicle showcased improvements in passenger protection, focusing particularly on systems adapted to protect young passengers. Recent developments in active and interactive safety systems were also added to ESF2009 for field tests in vehicle operation.
ESF2019 – (GLE-Class)
Built on the new GLE-Class chassis, the most recent Mercedes-Benz experimental safety vehicle, ESF 2019, was presented to the press by the company at its Technology Centre for Vehicle Safety in Sindelfingen in May, 2019 – the same site where the first ESV conference was held in 1971 – and later shown at the International ESV Conference in Eindhoven, Netherlands, in June, and finally at the Frankfurt Motor Show in September. This vehicle represents the very latest driving-safety technologies under development, including cooperative interactive safety systems, child safety, rear-seat safety and comfort, new Pre-Safe functions, communication with the vehicle’s surroundings and mechanisms to secure an accident scene, even if the vehicle’s occupants are unable to do so.
From Left: 2009 ESF2009; 1974 ESF24; 1973, ESF22a; 1972, ESF13; 1959, W111
2019, ESF2019
END SIDEBAR
Rollover testing a unibody W180 Ponton, 1950s.
Untertürkheim, 1967; a crude wooden test dummy used to simulate the impact of the driver against a steering wheel.
ABOVE: Safety steering-wheel patent drawing with impact absorber and telescopic steering column; series production began in August 1967.
The advantage of anti-lock brakes was first demonstrated in Untertürkheim in 1978 using the W116 S-Class, with (right) and without anti-lock braking.
The electronic components of the anti-lock braking system jointly developed by Daimler-Benz and Bosch.
Premiering in W124 models at the Frankfurt Motor Show in September 1985, a comprehensive package of advanced handling control systems, including automatic locking differential, acceleration skid control, and 4Matic automatic all-wheel drive, was later demonstrated to the press in February 1986.
Distronic Plus cruise control radar sensor (arrow), W209 CLK.
Blind Spot Assist uses radar to monitor areas alongside and behind the car, warning the driver when changing lanes.
Driver’s airbag and steering wheel/pedal cluster demonstrated in ESF 2019: The airbag expands over the top of the retracted steering wheel; pedals retract for safety and comfort.
During emergency braking, Adaptive Brake Lights flash rapidly, warning drivers behind.
With its Intelligent World Drive demonstration, Mercedes-Benz is using an S-Class-based vehicle to test automated driving functionality in real conditions on five continents. Here the vehicle confronts Australian traffic conditions in the city of Sydney.