Active Safety - Warning, Supporting, Acting: Accident Prevention through Assistance Systems

Jun 15, 2007
  • Mercedes assistance systems honed for real-life accident scenarios
  • Substantial decrease in the number of serious driver-related accidents, rear-end collisions, and accidents involving pedestrians
  • PRE-SAFE® Brake lessens accident severity by up to 40 percent
  • New blind-sport assistant ensures safe lane changes
  • Fatigue detection system undergoing field testing
Because of big advances in passive safety systems, the focus of development work is now increasingly shifting to the creation of preventive protection techniques such as PRE-SAFE® and the avoidance of accidents altogether. Mercedes-Benz will continue to contribute to this development in order to increase road safety.
High-performance assistance systems are helping to defuse dangerous driving situations and avoid accidents. With their help it is possible to determine if a driver fails to respond correctly or responds too late, and to correct such mistakes in a targeted manner.
The era of electronic assistants commenced with the introduction of the anti-lock braking system (ABS). “We weren’t satisfied with just building an outstanding brake. We wanted to do more so that drivers could remain in control of their cars when faced with dangerous driving situations,” said Daimler Board of Management member Professor Hans Scherenberg, when he presented the first ABS to an astonished public on December 9, 1970, and explained that the system would allow drivers to still make avoidance maneuvers even when slamming on the brakes. However, at the time it was still too early to use the system for everyday driving, as it proved to be difficult to raise the functioning prototype’s reliability and readiness to a point considered essential for series production. The main stumbling block was that a revolution in electronics had to occur first.
But the efforts eventually paid off in 1978, when Mercedes-Benz became the world’s first automaker to offer an anti-lock braking system. ABS was initially installed in the S-Class as an optional extra for 2,217.60 deutschmarks. The system became part of Mercedes-Benz’ standard equipment range in 1984, when a surcharge was no longer required for its installation in the 190 E 2.3-16 and the S- and SL-Class models. The anti-lock braking system has been offered as standard for all Mercedes passenger cars since October 1, 1992.
The system’s difficult but eventually successful production launch motivated the experts to strive for new heights. With the help of advanced microelectronics, the engineers managed to control the interplay of the longitudinal forces between the tires and the road surface. A new system known as acceleration skid control (ASR) allowed them to control these forces not only during braking maneuvers, but also when the car is accelerating. ASR celebrated its world premiere in 1987, naturally appearing first in a Mercedes-Benz.
From “transverse skid control” to the stability program
However, the engineers at Mercedes were not about to stop with what they had achieved to date, and their next objective was to improve safety in all types of driving situations, such as when cornering, evading obstacles or engaging in other types of transverse vehicle movements with a high risk of skidding. To achieve this aim, the company kicked off another ambitious development project in the early 1980s, bearing the working title of “Transverse Skid Control.” In this project, engineers from Mercedes-Benz and Bosch worked together to develop technical measures for monitoring a car’s skidding motions, which they then aimed to reduce by means of specific interventions in the operation of the vehicle’s chassis, engine and transmission.
Following preliminary testing and in-depth computer simulations, trials of the first test vehicles began in 1987. In subsequent years, the vehicles covered thousands of kilometers in tests. At the same time, transverse skid control demonstrated its suitability for everyday use in the driving simulator. The go-ahead for the system’s series development was given in 1992, and Mercedes-Benz was able to present the invention to the media on . Originally known as “dynamic handling control,” the system was shortly thereafter given the far better name of Electronic Stability Program, or ESP® for short.
This milestone in active safety was first installed in the top models of the CL‑, SL- and S-Class in spring 1995. In summer 1999, Mercedes-Benz became the first and to date only passenger car brand to install the stability program in all of its models as standard. In this regard, the brand is still exemplary today. Currently, about three-fourths of the new passenger vehicles registered in are equipped with the Electronic Stability Program. However, only about 40 percent of all new passenger cars in the European Union are fitted with the safety system.
“The system that we are presenting to you today will assist motorists in coping with driving errors and extraordinary situations, and thereby reduce the stress of driving. It will therefore contribute substantially to adapting motor vehicles to people’s capabilities. which is why we at Mercedes-Benz consider this development to be very important,” Mercedes Director Hermann Gaus told journalists in a farsighted statement in 1994.
Today, it’s very clear how accurate his assessment was, as ESP® demonstrably helps drivers avoid accidents, and thus, like ABS, seatbelts and airbags, contributes substantially to traffic safety.
ESP® provides big boost in safety
The system’s considerable safety potential becomes especially evident when analyzing so-called driver-related accidents, in which drivers lose control of their vehicles and begin skidding, for example. In three-fourths of driver-related accidents, the vehicles leave the road. The consequences are frequently severe, as over 40 percent of all traffic fatalities and 20 percent of injuries are caused by driver-related accidents.
After eight years of having the system included as standard equipment in Mercedes passenger cars, the Stuttgart-based brand has registered a significant decrease in driver-related accidents in which drivers lose control of their vehicles, skid and leave the road. The analysis of a representative sampling of the latest accident statistics shows that Mercedes passenger cars have been involved in serious driver-related accidents far less frequently than vehicles from other brands since being fitted with ESP® as standard equipment. The average share of newly registered Mercedes vehicles involved in such accidents in 1998/1999 was 20.7 percent. ESP® helped to reduce this figure by more than 42 percent in 2004/2005. At the same time, the share of passenger car models from other brands involved in these types of traffic accident fell by only about 15 percent.
If all automobiles were equipped with the stability system, more than 20,000 such serious accidents, which claim over 27,000 victims each year, could be prevented in Germany alone.
Moreover, ESPÒ also helps to reduce the extent of injuries to vehicle occupants in an accident. For example, because the system stabilizes vehicles in a skid, the risk of dangerous side collisions with trees, poles or other objects at roadsides is reduced. Following the installation of the stability program as standard equipment in Mercedes-Benz passenger cars, the proportion of collisions resulting in the most severe injuries fell from 15 to five percent.
The results of Mercedes-Benz accident studies also show that passenger cars equipped with ESP® roll over less frequently than vehicles not equipped with this safety system. Thanks to ESP®, the proportion of Mercedes-Benz vehicles involved in rollover accidents has decreased by around 12 percentage points. Studies conducted in the U.S. and Sweden also confirm the positive impact the system has had in reducing accidents or mitigating their consequences. The American Insurance Institute for Highway Safety, for example, has determined that ESP® can reduce the risk of fatal single-vehicle accidents by 56 percent. And the U.S. National Highway Traffic and Safety Administration (NHTSA) has come to the conclusion that ESP® reduces the risk of a single-vehicle accident by up to 67 percent and that between 5,300 and 9,600 lives could be saved in the United States each year if the system were installed in all vehicles.
Brake Assist reduces number of rear-end collisions
Brake Assist, which Mercedes-Benz was the first carmaker to introduce in 1996, has also proven to be an effective instrument for accident prevention. The system supports drivers who engage the brakes quickly enough but not hard enough in dangerous situations by ensuring maximum braking deceleration at lightning speed. Since 1997, Brake Assist has been standard equipment in all Mercedes passenger car models. On the basis of a representative sampling of the accident figures compiled by the Federal Statistical Office in Germany, Mercedes-Benz has determined the accident rate of rear-end collisions per 10,000 newly registered automobiles. The results show that the rate of such accidents involving Mercedes passengers cars dropped by eight percent to 9.7 following the installation of Brake Assist as standard equipment. By contrast, the rate for the vehicles from other brands remained relatively unchanged during this period.
Rear-end collisions are among the most frequent and severe types of traffic accidents. In the European Union, care and treatment of the car occupants injured in such accidents costs up to ten billion euros a year. The more widespread use of Brake Assist could prevent thousands of rear-end collisions and pedestrian-related accidents each year. However, only about 58 percent of all new vehicles are currently equipped with braking assistance in Europe.
Just as impressive is Brake Assist’s help in the prevention of accidents involving pedestrians. The evaluation of accident statistics showed that severe pedestrian collisions accounted for 36.4 percent of the accidents in Mercedes passenger cars lacking BAS. This figure dropped by 13 percent after BAS was installed as standard equipment. For the automobiles form other brands, the share of pedestrian-related accidents resulting in fatalities or severe injuries decreased by only one percent during this time period.
Brake Assist with radar delivers even better performance
Seconds - sometimes even fractions of a second - make the difference between an accident happening and its being averted. In these critical moments it is crucial both to recognize the danger in good time and to act quickly and decisively to avoid a collision. Cutting-edge Mercedes technology can provide effective support for the driver on both counts, significantly improving road safety thanks to Brake Assist PLUS and the new PRE-SAFE® Brake.
On recognizing a potential accident situation, help is provided to both systems by the near-area radar sensors behind the front bumper and a long-range radar in the radiator grille. Together, they continually monitor the traffic activity in front of the car. The near-range radar (24 gigahertz) operates with a range of 30 meters and an effective angle of 80 degrees, while the long-distance radar (77 gigahertz) has an opening angle of nine degrees and is capable of scanning a three-lane, 150 meter-long stretch of highway. Computers assess the data from both radar systems. If the distance to the car in front is not sufficient, a red warning symbol lights up in the instrument cluster.
If the vehicle in front, which is registered by the radar, brakes suddenly, creating the risk of a collision, an additional warning tone also sounds. This is the clear and unmistakable prompt for the driver to brake. The driver is assisted by Brake Assist PLUS (BAS PLUS) - as soon as the first warning tone sounds, the system automatically determines the brake pressure required in this situation to prevent the collision. In other words, the system helps the driver to recognize the risk and makes the calculated brake boosting force instantly available, even if the driver does not step on the brake forcefully enough. Depending on the speed and distance, BAS PLUS therefore allows controlled, targeted braking. If necessary, the system increases the braking force up to full braking.
Wide-ranging tests of the effectiveness of Brake Assist PLUS carried out in the simulator show that this system reduces the accident rate in typical situations involving the risk of a rear-end collision from 44 to 11 percent. However, it should be noted that support is only provided by BAS PLUS if the driver gives the braking command - by stepping on the brake pedal.
Automatic partial braking when an accident is unavoidable
Unfortunately, drivers in practice do not always react as quickly as is needed at critical moments - for example because they are distracted and fail to register the warning signals. The newly developed PRE-SAFE® Brake intervenes in situations such as these, automatically braking the CL-Class or S-Class if there is acute danger of an accident. The Mercedes experts call this “autonomous partial braking,” an automatic braking process with deceleration of up to 0.4 g (approx. four m/s²), in other words around 40 percent of the maximum braking performance.
Just how quickly the assistance systems recognize a potential accident situation, warn the driver and provide driver assistance or, if the danger is acute, intervene themselves, can be seen by looking at a timeline representing a typical rear-end collision situation:
Autonomous PRE-SAFE® partial braking has a twofold effect:
The intervention of the PRE-SAFE® Brake makes distracted drivers aware of the situation, alerting them to the acute danger and indicating that immediate action is required. The driver is further aided in the attempt to avert the accident by the S-Class’ safety systems: During emergency braking, Brake Assist PLUS instantly calculates the optimum braking force for the given situation; if the car veers rapidly to one side, ESPÒ stabilizes the vehicle and reduces the risk of skidding.
If the collision cannot be avoided, the PRE-SAFE® Brake helps to minimize the consequences of the accident. The importance of this “electronic crumple zone” for occupant protection was determined by test engineers from Germany’s ADAC automobile association. Driving tests conducted by the engineers showed that autonomous partial braking reduced the impact speed by 12.5 km/h. In other words, instead of making impact at 50 km/h, for example, the vehicle equipped with the PRE-SAFE® Brake struck the rear of another car at 37.5 km/h, reducing the force of impact on the occupants in the front by about 30 percent, and by 45 percent for occupants in the rear seat. In its final assessment, the ADAC concluded: “The crash test demonstrates: The ‘thinking brake’ helps.”
In the future, this technology could also serve as a basis for an autonomous braking system that automatically implements full braking when there is acute danger of an accident, which can greatly reduce the force of impact.
Warning drivers against risky lane changes
The Mercedes engineers are also working on other assistance systems that focus on different problem areas revealed by the accident statistics. Their new systems are intended, for example, to make lane changes safer, improve safety at intersections and support the driver when turning into another street or road. They include the use of automatic vehicle and object recognition based on cutting-edge video technology.
A newly developed Mercedes assistance system makes changing lanes safer for drivers. The system uses six short-range radar sensors that monitor both sides of the area behind the vehicle. This makes it possible for them to detect another vehicle moving in the “blind spot” in a parallel lane. In such situations, the system warns the driver by means of a red warning light in the glass of the exterior mirror. If the driver fails to notice the red light and uses the turn signal to indicate a lane change, the warning light begins to blink and a warning alarm is also sounded.
Another focal point in the development of driver assistance systems is the issue of driver fatigue. Many serious accidents occur because drivers are tired and experience bouts of microsleep. Mercedes-Benz is developing a system that recognizes signs of fatigue and warns the driver.
One million test kilometers on two continents
Mercedes driver-assistance systems are designed to handle the situations actually encountered in everyday driving and are thoroughly tested under such conditions. These extensive measures are indispensable for ensuring outstanding reliability in all driving situations.
The new radar-based safety systems for the CL-Class and the S-Class, for example, have completed an unprecedented test program. In order to assess the technology in everyday traffic, Mercedes-Benz has a total of 30 test cars in operation in Germany and the U.S. To date, more than 500 drivers have driven Mercedes-Benz vehicles for a total of approximately one million kilometers of such practice-oriented testing. Cameras and computers on board the test cars log critical traffic situations and enable precise analysis of how reliably the systems work and how they support the drivers.
In the laboratory the cutting-edge “hardware in the loop” test procedure combines the advantages of practical testing with those of computer simulation. Brake Assist PLUS and the PRE-SAFE® Brake have completed intensive endurance tests on the test rig - in a virtual world but using data from real traffic situations. The method allows the hardware intended for use in series-produced vehicles - in other words the system components such as control units, hydraulic units and sensors - to be included in the test runs. Powerful computers feed the units with sensor data from simulated traffic situations and log the control commands with which the components respond.
In this way, it was possible to confront the PRE-SAFE® Brake's control electronics system with thousands of real traffic situations over a short period of time and thereby demonstrate its reliability.