Mercedes-Benz Unveils Safety Concept At International Auto Show (10/01)

Mercedes-Benz, at the 59th International Automobile Fair in Frankfurt (September 13-23), unveiled a concept for a vehicle that can detect an imminent collision and engage occupant protection systems before it occurs.

Known as PRE-SAFE® (for "Preventive Occupant Safety''), the experimental and proprietary safety concept combines hazard-detection technology currently in use in Mercedes-Benz passenger vehicles with new types of seatbelt tensioners and automatically adjusting seats. Future versions of the concept would include active body structure and interior components, as well. Mercedes-Benz has already developed the sensor systems and actual protective components of the PRE-SAFE concept to the point that they can be evaluated in test vehicles.

Company safety experts believe that most of the potential in passive safety technology has now been exploited and that further advances will require new concepts -- like the more proactive PRE-SAFE.

The principles behind PRE-SAFE are based on the findings of Mercedes-Benz accident researchers, which reveal that in approximately two-thirds of all traffic accidents (as studied in Germany) there is a relatively long time interval between the driver's recognition of an impending accident and the impact itself. The researchers conclude that new technology can activate the vehicle's protection systems during this interval.

"Our present protection systems such as airbags, side curtain airbags or belt tensioners must ensure safety in a matter of milliseconds, even though accident recognition can be measured in seconds,'' explains Dr. Rodolf Schoneburg, the head of safety development at Mercedes. "Making use of this interval opens up new dimensions in occupant protection.''

The research team at Mercedes-Benz has already been testing a number of concept systems based on PRE-SAFE systems, including automatic extending bumpers, "smart'' crash boxes in the front-end structure, and even active interior components such as movable interior door panels, sensor-controlled seats, and other ideas for preventive occupant protection. An added benefit of these types of systems: if the collision is successfully avoided at the last moment, the PRE-SAFE systems could reset themselves to their original status, thereby avoiding expensive repairs.

Company researchers believe that the early recognition of an impending accident and the development of suitable, situation-related occupant protection technology represent the greatest safety engineering challenge of the next few years. Systems will need to rely on specialized sensors that continuously monitor the driver, vehicle, and road surface and can recognize critical situations at an early stage to help prevent accidents. PRE-SAFE is a first step toward meeting this challenge, that builds on several subsystems that are already standard equipment in some current Mercedes models. The anti-lock braking system (ABS), Brake Assist (BAS), and the Electronic Stability Program (ESP®) driving safety systems form the basis for the innovative PRE-SAFE concept.

Protection Can Begin Before an Accident Occurs

In a future PRE-SAFE equipped Mercedes vehicle, the new occupant protection systems would go into action when sensors in the car detect that the vehicle is on a collision course with another vehicle. Even before the driver has time to react and apply the brakes, the seatbelts will tension and restrain the driver's and passengers' torsos, preventing their bodies from moving forward during the ensuing braking maneuver and ensuring a safe seating position. At the same time, the seat cushions of the front passenger and rear seats will automatically tilt to the rear, while the door panels will move into the car's interior and mold themselves around the occupants' hips like protective shields.

Accident analyses by Mercedes-Benz researchers show that in two-thirds of all collisions, enough time elapses before the impact to activate such protective systems. In roughly 60 percent of the more than 1,000 reconstructed accidents, the vehicles involved were in a dynamic state that indicated an impending impact.

"For Mercedes, PRE-SAFE means the logical continuation of our long-held safety philosophy,'' says Dr. Schoneburg. "In the future we will also be able to use the time interval between recognizing a dangerous situation and the point at which the actual impact occurs to prepare the car for the impending crash and therefore give the occupants the best possible protection. Our previous protection concept will therefore be supplemented with an additional PRE-SAFE phase.''

Warning phase

Sensors on the axles and chassis monitor the vehicle's behavior. When the vehicle's dynamic limits are reached, a yellow warning symbol lights up in the cockpit.

Assistance Phase

Standard dynamic systems such as ABS, Brake Assist and ESP® automatically intervene in critical situations and help the driver maintain control.

PRE-SAFE Phase

Sensors detect the enhanced probability of an accident. Various safety systems are activated as a precaution to prepare for the possible accident and prepare both the vehicle and its occupants. If the accident is avoided, the PRE-SAFE systems are automatically reset to their original status.

Light Impact

In the case of impacts up to about 9 mph, the bumpers and crash boxes in the front-end module absorb the impact energy. Sensors monitor impact severity and prevent activation of the airbags if their additional protection is not required.

Minor Accident

During a more serious impact, robust structural members in the front end, sides, and rear end of the vehicle absorb energy and distribute the forces over a wide area. The belt tensioners go into action. Depending on impact severity, the front airbags inflate less than fully to ensure optimal occupant protection. Door-mounted and side curtain airbags provide protection during a side impact. The automatic front passenger and BabySmart® child safety seat recognition system prevents activation of the front
passenger airbag and belt tensioner if they are not required. The fuel supply to the engine is also cut off.

Serious Accident

In the event of even greater risk to the occupants a second, additional stage is activated in the front airbags. At the same time, the belt force limiters are activated to prevent possible internal injuries.

Recovery Phase

The doors are automatically unlocked after the accident. The Tele Aid emergency call system (now available on all Mercedes models) alerts emergency services and guides them to the scene of the accident. The hazard warning flasher system is switched on.

The sensors on which PRE-SAFE relies not only recognize a critical dynamic situation, but also provide data that the computer uses to predict an impending accident with a high degree of probability. Mercedes-Benz' multi-stage approach features four distinct sub-systems:

On the basis of these sensor data, a powerful onboard computer prepares the vehicle components and vehicle structure for an impending accident. This could involve, for example, extending the bumpers and activating the crash boxes in the front-end structure. Depending on accident severity, these systems would generate forces suitable to absorb a large proportion of the impact energy before it can act on the vehicle occupants.

In the event of an impending side impact with a higher vehicle, such as a large SUV, van or truck, the computer would engage the Active Body Control system (currently used on the Mercedes-Benz CL-Class coupes and certain S-Class sedans) to actually raise the vehicle body and enhance its crash compatibility with the colliding vehicle. Another countermeasure is automatic closure of the sunroof, to prevent the occupants from being ejected in the event of a rollover.

Interior: Seats, Steering Wheel and Door Panels Automatically In Protection Position

PRE-SAFE places emphasis on new safety systems in the vehicle interior that aim to ensure occupants are placed in the most protected position possible even before the impact. For example:

Mercedes-Benz has set its safety objectives even higher for the long-term future. Company engineers talk about a "thinking'' car that is able to recognize its surroundings. This recognition would extend not only to the road ahead or to other vehicles, but would include traffic lights, road signs, and pedestrians as well. Mercedes' aim for its cars of the future is to be able to interpret entire traffic scenarios and, if necessary, automatically initiate PRE-SAFE style accident prevention measures. All of which underscores the idea that smarter cars can mean safer people.