New Mercedes-Benz S-Class Thinking ahead

Press Release

PRE-SAFE® and Brake Assist PLUS: Milestones in passenger car safety - now even more effective through new technology

• Predictive Brake Assist PLUS with radar technology

• Accident rate down from 44 to 11 percent in simulator tests

• Newly developed close-proximity radar combined with DISTRONIC

• Brake-power support in accordance with the situation surrounding an impending accident

• Precautionary PRE-SAFE® vehicle-occupant protection with new features

Seven prizes and awards in just three years; praise from all quarters - these are the elements of the success story of the PRE-SAFE® precautionary occupant protection system to date. Mercedes-Benz first presented the system to the public in 2002, and since then PRE-SAFE® has proven its effectiveness in more than 140,000 S-Class saloons.

PRE-SAFE® recognizes a potential accident situation in its early stages, after which it prepares the vehicle and its occupants for the expected impact. If, for example, the vehicle is in danger of skidding, or the driver is forced to brake hard, PRE-SAFE® will tighten the front seatbelts as a precautionary measure and also adjust the passenger seat into the most favourable position. If necessary, it will even close the vehicle’s sunroof. The system also adjusts the electronically controlled individual seats in the rear of the vehicle. Such precautionary measures ensure that seatbelts and airbags offer the best possible protection in the event of an impact. If the driver is able to avoid the accident, PRE-SAFE® will loosen up the seatbelts again and passengers can return their seats and the sunroof to their original positions. The system is then ready to go into action again if necessary.

The PRE-SAFE® early warning system for accidents is based on a unique combination of active and passive safety elements. PRE-SAFE® is networked with standard-equipment safety systems such as Brake Assist (BAS) and the Electronic Stability Program (ESP®), whose sensors are able to recognize potentially dangerous driving manoeuvres. The relevant data is sent to an electronic control unit that implements the precautionary safety measures if certain values are exceeded.

Three years after the world premiere of this pioneering invention, with which Mercedes-Benz launched a new era in passenger car safety, the second generation of PRE-SAFE® is set to go into series production. Engineers at the Stuttgart-based premium brand have succeeded in further perfecting the interaction between active and passive safety systems. As a result, a refined Brake Assist PLUS and additional PRE-SAFE® features will offer even more possibilities for preventing accidents and protecting passengers in the new Mercedes-Benz S-Class in the future.

Brake Assist: Effectiveness in preventing accidents proved a million times over

Back in 1992, Mercedes engineers conducting tests with a driving simulator discovered that although most drivers react quickly in dangerous situations, they often fail to apply sufficient pressure to the brake pedal. This means that the braking system’s capability is not fully exploited, something which significantly increases the braking distance. The engineers’ discovery led to the development of Brake Assist, which went into series production in 1996 and has been standard equipment in all Mercedes-Benz passenger cars since 1997.

The system can interpret a certain speed at which the brake pedal is depressed as indicating an emergency situation, in which case it generates maximum braking power within fractions of a second. This leads to a significant reduction in braking distance � up to 45 per cent, for example, when the vehicle is travelling on a dry road at a speed of 100 km/h.

Brake Assist has proven itself more than a million times over since its inception. It not only helps prevent rear-end collisions but also makes an effective contribution to protecting pedestrians, as revealed in a study conducted by Mercedes-Benz with a driving simulator, in which 55 men and women took a simulated drive through a town at a speed of 50 km/h, during which a child suddenly ran into the street. The only way to avoid hitting the child was to initiate an emergency braking manoeuvre. The test showed that drivers supported by Brake Assist had far fewer accidents than those drivers who did not have the system; the overall accident rate was reduced by 26 percentage points through the use of Brake Assist.

Brake Assist PLUS: Two radar systems for monitoring the road ahead

Mercedes-Benz will expand Brake Assist’s features in the future to create a predictive system that provides even more effective support for drivers in dangerous situations. Radar technology will be used to determine the distance to vehicles ahead, warn drivers when they get too close, and provide the necessary braking power if it appears that a collision is unavoidable. In those situations where drivers are forced to brake, the new Brake Assist PLUS system will calculate and generate the braking force needed for a given situation within fractions of a second.

While the conventional Brake Assist requires a reflex activation of the brake pedal, the new system recognises the driver’s intention to brake when he or she puts clear pressure on the pedal, after which it automatically optimises the braking pressure. One of the key preconditions for preventing rear-end collisions is thus fulfilled: the best possible braking deceleration for each situation.

Mercedes-Benz has conducted extensive tests with the new technology, in both a driving simulator and under real conditions:

• The driving-simulator tests involved a total of 100 drivers, each of whom drove for 40 minutes and were confronted with several critical situations on motorways and rural roads, whereby emergency stops were the only way to prevent an accident. The result was that 44 per cent of the simulated drives taken with conventional brake technology resulted in accidents, but only 11 per cent of those in which Brake Assist PLUS was used. The new system’s performance was demonstrated especially clearly during a drive in heavy traffic at 80 km/h along a rural road. When the car in front braked suddenly, 93 percent of all cases in which the radar-supported Brake Assist was used remained accident-free; without this system, rear-end collisions occurred in around half of all tests. Even in cases where a collision was inevitable due to the driver reacting too late, the new system helped to reduce the severity of the accident. The latter aspect can be demonstrated through the speed at which the collisions occurred, with Brake Assist PLUS reducing this speed from 47 to 26 km/h.

• The practical tests, which were conducted in Europe and the U.S., involved more than 200 men and women who drove two dozen test vehicles over a total distance of more than 400,000 kilometres. Data on these trips was collected with the help of state-of-the-art measurement and video technology. Analysis of the data and video sequences showed that Brake Assist PLUS also effectively enhances safety under real conditions.

Radar technology: Large angle of coverage over short radius

The predictive Brake Assist uses two radar systems to monitor the traffic situation in front of the vehicle, whereby a newly developed close-proximity radar based on 24-Gigahertz technology works in tandem with the tried and proven 77-Gigahertz radar employed in the DISTRONIC proximity cruise control system. The two systems complement each other well: Whereas the DISTRONIC radar is designed to be able to track three motorway lanes over a distance of up to 150 metres with an angle of nine degrees, the new 24-Gigahertz radar uses an angle of 80 degrees to monitor the immediate area (30 metres) in front of the vehicle.

Accident types: Engineers focusing on rear-end collisions

With Brake Assist PLUS, which will be ready to go into series production in just a few months, Mercedes-Benz is once again underscoring its role as a trendsetter for road safety. As was the case with the airbag, seatbelt tensioner, ESP® and other pioneering safety systems, development of the predictive Brake Assist system also focused on the types of accidents that commonly occur under real conditions. More specifically, the researchers took into consideration the high number of rear-end collisions, which account for 17 percent of all traffic accidents that result in fatalities and injuries in Germany.

In the U.S., rear-end collisions account for 31 per cent of all accidents that result in deaths and injuries, according to statistics from the National Highway Traffic Safety Administration (NHTSA).

Precautionary occupant protection: BAS PLUS and PRE-SAFE® in tandem

Networking Brake Assist PLUS with PRE-SAFE® has opened up new dimensions in passenger car safety: Radar-based sensors make it possible to recognize potentially dangerous situations before they actually occur and then implement precautionary protection measures for vehicle occupants more quickly than was previously the case.

The system in use today engages during emergency braking manoeuvres (i.e. a reflexive reaction on the part of the driver). In the future, however, it will also be possible for PRE-SAFE® to go into action when Brake Assist PLUS has determined through its calculations that a rear-end collision is imminent - and that the driver’s braking manoeuvre has resulted in a certain deceleration value being exceeded.

The system will then tighten the front seatbelts and adjust the front and rear passenger seats as precautionary measures, thereby preparing occupants for a possible impact in such a way that seatbelts and airbags can provide the best possible protection.

PRE-SAFE®: Inflatable support upholstery in vehicle seats

In the future, Mercedes-Benz will supplement the proven PRE-SAFE® features with additional precautionary measures. These will prepare occupants for potential accidents even more extensively � always with the overall objective of ensuring that seatbelts, seatbelt tensioners, belt force limiters and airbags will all work perfectly in the event of a crash.

For example, a newly developed multi-contour seat makes it possible to more effectively fix the position of the driver, front passenger and rear occupants, and thus significantly restrict dangerous movements of the upper body in a crash. When the PRE-SAFE® control unit recognizes a critical driving situation, it will activate within seconds air cushions in the seats (front) and backrests (front and rear), which envelop and support vehicle occupants.

Rear-end collision tests conducted at the Mercedes-Benz Technology Center show that this new PRE-SAFE® feature and the precautionary tightening of seatbelts increase the distance of the occupants’ shoulders to the door trim by up to 40 millimetres at a lateral acceleration of 0.6 g. This enables the sidebag to provide even more protection.

Mercedes engineers will also be further improving the brand’s standard windowbags in the future by incorporating an additional precautionary feature: If the car is in danger of skidding and an accident thus appears likely, PRE-SAFE® will automatically close the side windows, which hold up the windowbags that inflate in the event of a side impact or rollover. This new PRE-SAFE® features also reduces the risk of occupants being thrown from the vehicle or objects flying into the car from outside.

Overview of all current and future PRE-SAFE® features:

* Reversible: If the anticipated accident does not occur, the systems will automatically return the components to their original positions.

Outlook: PRE-SAFE® support upholstery for the front passenger; autonomous braking systems

Mercedes-Benz will continue to refine its precautionary occupant protection systems over the next few years. Future PRE-SAFE® concepts for better preparing vehicle occupants for impending accidents will, for example, include a knee-protection system that automatically folds out from under the dashboard, providing support to the front passenger and reducing stress on the legs in the event of a collision. Like the PRE-SAFE® seatbelt tensioner, the knee protection system is also completely reversible, folding back in underneath the dashboard if the accident is avoided. In a similar vein, it might be possible to design door trim panels that move in towards occupants before a crash occurs, thus keeping them further away from parts of the vehicle body that could be forced into the interior in the event of a side impact. Fold-out trim panels on the inside of the B-pillar could also perform this type of support function.

When PRE-SAFE® developers look towards the future, they also imagine a protective system that can adapt to the individual parameters of vehicle occupants. For example, it might be possible for drivers and passengers to enter into the vehicle’s onboard computer personal data such as height, weight, gender, age, and any illnesses they may have. The system could then use this data to customize for each vehicle occupant elements such as volume flows in airbag inflation, level of seatbelt tensioning, or the functioning of the belt-tension limiter. Other PRE-SAFE® functions � for example, automatic seat repositioning prior to a crash � could also be regulated according to an occupant’s size.

There’s great potential for the further development of Brake Assist PLUS as well: Mercedes engineers are using radar sensors as the basis for developing a system that will precisely monitor both the traffic situation in front of the vehicle and the vehicle drivers themselves. If, for example, the driver fails to react when there’s danger of a rear-end collision (and a warning to this effect has also been issued), the new system would autonomously engage a partial braking manoeuvre and simultaneously activate the PRE-SAFE® features for the vehicle’s interior. This autonomous braking with up to 0.4 g deceleration would force the driver to act � in other words, to brake hard. After that, Brake Assist PLUS would provide the necessary braking support with the aim of preventing the accident, or at least reducing impact energy if the accident becomes unavoidable.

This new type of technology could also be used to develop an autonomous braking system that would automatically engage if an accident appeared imminent, at first initiating an emergency stop. Such a system would go a long way towards the “Vision of Accident-Free Driving� � the long-term goal of Mercedes-Benz safety engineers.