For Mercedes-Benz, automotive safety is not merely a matter of crash tests during which specific types of impact are simulated under laboratory conditions. The specialists in Sindelfingen are primarily interested in reality: in what actually happens in traffic situations and accidents, and in the many critical situations where cars must prove their capabilities. The comprehensive Mercedes-Benz concept takes all the aspects of safe driving into account – from accident prevention to occupant protection and the quickest possible recovery of accident victims.
One of the mainstays of this philosophy is the anticipatory occupant protection system PRE-SAFE®, which is standard equipment in the new CL-Class. Accordingly the Mercedes Coupé features a safety technology which no other car in this class offers, worldwide. For the first time this system is able to create a synergy between active and passive safety: on the basis of sensor information from active handling safety systems, which register the danger of a skid or very heavy braking within milliseconds, PRE-SAFE® uses the time between detection of a potential accident and activation of the protective systems in the vehicle interior. During this interval PRE-SAFE® prepares the occupants for the impending collision as a precaution.
In other words, PRE-SAFE® gives the car reflexes. When danger is detected, the new CL-Class responds as reflexively as a living being and activates the appropriate protective measures to avoid the risk of injuries or reduce their severity. This Mercedes invention is in line with the findings of accident researchers, which show that more than two thirds of all serious accidents are preceded by critical driving manoeuvres that allow an impending collision to be predicted in advance. In the new CL-Class, PRE-SAFE® uses this advance accident detection phase, which can have a duration of several seconds in some cases, to ...
- move the front passenger seat to a more favourable position with respect to height and fore-and-aft adjustment, as well as cushion and backrest angle, during emergency braking, so that the seat belt and airbag are able to work most effectively during an impact, and to inflate the air chambers in the dynamic multicontour seats (optional) to support the driver and front passenger and press them more firmly into their seats.
additionally close the front side windows and sliding sunroof if the car starts to skid, so that the occupants are not thrown out and the windowbags have better support during a side impact or rollover.
Automatic partial braking when a collision is imminent
The newly developed PRE-SAFE® Brake system improves this preventive occupant protection even further. This system, which is absolutely unique worldwide in the extent of its functions, automatically brakes the CL-Class before an impending accident and operates in tandem with the Brake Assist PLUS (BAS PLUS) system introduced last year, which warns the driver of an imminent rear-end collision with visual and audible signals and automatically calculates the required braking pressure to prevent an accident. This braking-power support is available as soon as the brake pedal is operated.
The PRE-SAFE® Brake system goes one step further: if the driver does not react to the BAS PLUS warnings, the PRE-SAFE® Brake system triggers automatic partial braking where an accident is imminent and slow the CL Class down at a rate of up to 0.4 g (around 4 m/s²), corresponding to around 40 percent of the total braking power. The automatic partial braking provides the driver with another clear warning to act. If the driver then immediately applies the brakes, the maximum braking force is available and the accident can - depending on the situation - be averted at the last moment. If an accident is unavoidable, the PRE-SAFE® Brake system reduces the impact severity and, in turn, the risk of injury to the vehicle occupants.
The anticipatory PRE-SAFE® measures on board the new Mercedes Coupé are also activated automatically when the PRE-SAFE® Brake system goes into action: as soon as the system commences automatic partial braking, the supporting bolsters in the dynamic multicontour seats are inflated, the seat cushion and backrest angles are adapted and the front passenger seat is moved to the most favourable position.
Radar sensors in the bumper and behind the radiator grille
The anticipatory Brake Assist PLUS and the new PRE-SAFE® Brake system are part of the DISTRONIC PLUS equipment package. In addition to the 77 Gigahertz long-range radar of the proximity control system, these systems use newly developed short-range radar based on 24 Gigahertz technology. While the DISTRONIC radar is configured to monitor three lanes of a motorway up to a range of 150 metres with a scanning angle of nine degrees, the new 24 Gigahertz radar monitors the area immediately in front of the vehicle to a range of 30 metres and with a scanning angle of 80 degrees.
Accident severity reduced by 40 percent
Mercedes-Benz has intensively tested the effectiveness of the new PRE-SAFE® Brake system. In the DaimlerChrysler Research driving simulator in Berlin, Mercedes engineers conducted a series of tests with 70 drivers who were deliberately distracted by an accident on the opposite carriageway during their journey, while the traffic ahead of them suddenly braked at the same time.
The results of these tests demonstrate the increased safety made possible by the state-of-the-art support systems in the CL-Class: thanks to the rapid reaction of the drivers and the help of BAS PLUS with the PRE-SAFE® brakes, an accident was avoided during 70 percent of these journeys. In one third of these simulator tests the participants were unable to prevent an accident. In these cases the automatic partial braking function ensured a reduction of around 40 percent in impact severity.
Flashing brake lights: effective warning when danger threatens
Mercedes-Benz has developed flashing brake lights as a further contribution to the prevention of rear-end collisions. These are standard equipment in the new CL-Class. If the driver is obliged to brake hard from a speed of more than 50 km/h, or if Brake Assist is activated to support the driver in an emergency, the brake lights flash to warn traffic following behind. If the CL-Class is brought to a standstill after such an emergency braking manoeuvre, the brake lights revert to continuous operation and the hazard warning flashers are switched on at the same time.
Studies carried out by Mercedes engineers show that drivers’ braking reaction time can be shortened by up to 0.2 seconds on average if a flashing red warning light is substituted for a conventional brake light in emergency braking situations. As a result, the braking distance can be reduced by around 4.4 metres at a speed of 80 km/h, and by as much as 5.5 metres at 100 km/h.
ABS, ASR, ESP®, Brake Assist – all these are further driving safety systems on board the new CL-Class which can effectively contribute to accident prevention.
Night view assist: even better visibility at night
Mercedes-Benz has developed the night view assist system to improve driving safety even further, especially during the hours of darkness. This increases the driver’s range of visibility to up to 200 metres to reduce his workload when driving at night. This means that the system provides roughly the same range of visibility as high beam headlamps – but without dazzling oncoming traffic.
Night view assist, which celebrated its debut in the S-Class in autumn 2005 and is also available for the CL Coupé, features two additional, infrared headlamps. Their light is invisible to the human eye, and therefore does not dazzle oncoming drivers. An infrared-sensitive camera on the inside of the windscreen shows the scene ahead of the vehicle on a display in the instrument cluster of the luxury Coupé, enabling road signs, pedestrians, cyclists, debris or other obstacles in the road to be identified much sooner.
When night view assist is active, the infrared headlamps are automatically switched on when a speed of 15 km/h is reached and remain on when braking down to about 10 km/h.
As soon as night view assist is activated, the display in the centre of the instrument cluster switches over to show the camera image. The large eight-inch display is directly in the driver’s field of vision, and provides a clear greyscale image of the road ahead. The driver is able to glance down at the infrared image regularly, monitor the situation ahead of the vehicle and adapt his style of driving accordingly.
Up to 125 percent increase in safety
Mercedes engineers have examined the capabilities of this technology in a series of practical trials. During comparative test drives with low-beam bi-xenon headlamps and the new night view assist system, male and female test drivers recognised obstacles in the road much sooner when assisted by the infrared light system. During tests, drivers were already able to discern test dummies at the roadside dressed in light-coloured clothing at a range of around 210 metres, which is about 41 metres sooner than with low-beam bi-xenon headlamps.
The system proves even more effective in the case of pedestrians in dark clothing. In these situations the night view assist system already enabled the drivers to identify the test dummies at a range of around 164 metres, compared with only at about 72 metres when driving with low-beam bi-xenon headlamps alone. This represents a safety improvement of no less than 125 percent.
Even when the headlamps of oncoming vehicles dazzle the driver and severely obscure the view, visibility is much better with this assistance system: a test dummy in light-coloured clothing standing at the road edge 50 metres behind an oncoming vehicle was detected from an average distance of 140 metres with the help of night view assist – around 53 metres sooner than with low-beam bi-xenon headlamps.
The state-of-the-art CMOS sensor (Complementary Metal Oxide Semiconductor) and the infrared camera specially developed for Mercedes-Benz are able to reduce dazzle by electronic means, while enhancing the rest of the image to ensure that even smaller details are easily recognised.
Important contribution to safer driving in the dark
Night view assist is able to contribute greatly to improved road safety, as accident analyses carried out by Mercedes-Benz have confirmed: on the basis of data obtained from a joint accident research project conducted by German vehicle manufacturers and the federal office for roads and traffic, specialists at Mercedes-Benz analysed accidents occurring during the hours of darkness and found that the night view assist system has a very high safety potential.
The risk of serious injury in road traffic is much greater in twilight and in the dark than during daylight hours. Collisions at night are predominantly driver-induced accidents during which drivers lose control of their vehicles – often because they have not recognised the course of the road soon enough in the dark, and failed to adjust their speed. As a result around half of the vehicles in question leave the road, while more than one quarter collide with oncoming traffic. Night view assist can also help to improve the safety of pedestrians. According to German accident statistics, more than 55 percent of fatal accidents involving pedestrians occur in twilight or at night.
Intelligent Light System: latest lighting technology as standard
The Intelligent Light System developed by Mercedes-Benz also contributes to driving safety at night. This represents the most advanced headlamp technology currently available, and is standard equipment in the new CL-Class. This intelligent lighting system is based on powerful bi-xenon headlamps. These are variably controllable, and are networked with other electronic control units on board the new luxury Coupé, from which the headlamps obtain information about the current driving situation and distribute their beam patterns accordingly.
The familiar low-beam headlamps with their well-proven, asymmetrical light distribution are replaced by the new country road mode, which illuminates the driver’s-side edge of the road more widely and brightly than before. In the dark, this enables the driver to appraise the situation and respond more rapidly when other road users cross his path.
Motorway mode, which comes on automatically when driving above 90 km/h, increases the driver’s range of vision by up to 60 percent. This lighting function is activated in two stages: the Intelligent Light System first increases the output of the bi-xenon lamps from 35 to 38 watts, thereby increasing the light intensity and providing noticeably better illumination of the road ahead and the side verges. The second stage of motorway mode becomes available at 110 km/h and above. The beam of the bi-xenon module on the driver’s side is elevated slightly, while the high-beam spotlights of the CL-Class are switched on as well. A baffle in front of these spotlamps projects a light/dark cutoff onto the road to prevent oncoming drivers from being dazzled.
The new motorway mode has a range of around 120 metres, and the driver is able to see about 50 metres further at the centre of this cone of light than with conventional low-beam headlamps.
Headlamp automatically pivots outwards
With the enhanced fog lamps, Mercedes-Benz also provides drivers with better orientation in adverse weather conditions. This new lighting function is activated at speeds below 70 km/h, as soon as the rear fog light is switched on. The variable headlamp technology of the Intelligent Light System makes it possible to pivot the bi-xenon headlamp on the driver’s side outwards by eight degrees, while lowering its beam. This illuminates that side of the road more brightly and reduces the glare from reflected light in foggy conditions. The enhanced fog lamp function remains active up to a speed of 100 km/h.
The Intelligent Light System also includes the active headlamp and cornering light functions. These are switched on automatically: depending on the steering angle, yaw rate and vehicle speed, with the active headlamp function the headlamps pivot sideways by up to 15 degrees in fractions of a second, thereby greatly improving road illumination. On a gradual bend with a radius of 190 metres, the driver is able to see 25 metres further than with conventional low-beam headlamps thanks to this system. This function operates with both low and main-beam headlamps.
The cornering light function integrated into the main headlamps improves safety when entering junctions, openings and tight bends. It is automatically activated if the driver operates the indicators at a speed below 40 km/h or turns the steering wheel at a speed below 70 km/h. The headlamps then illuminate the side area ahead of the vehicle to a range of around 30 metres at an angle of up to 65 degrees.
The new, adaptive headlamp technology has been made possible by a ruling by the UN Economic Commission for Europe (ECE), which also applies within the European Union. Mercedes-Benz is the world’s first automotive brand to offer intelligent car headlamps.
Passive safety: to the highest Mercedes standards
The new CL-Class has an equally pioneering role in the field of passive safety. This is mainly due to the sophisticated bodyshell structure and highly effective restraint systems.
The forces generated during a frontal impact are dissipated at several levels to ensure that the passenger cell remains substantially undamaged. The front-end module and the so-called integral member, on which the engine, steering and front axle are mounted, join the front side members and the second level of side members together. During a frontal crash this creates two important energy dissipation channels which substantially contribute to occupant protection in the CL-Class. At the same time the robust, multi-skinned side members are able to absorb large forces and direct impact energy past the passenger cell. During severe offset collisions, the front wheel affected is braced by a specially designed energy-absorbing element acting as a forward extension of the side member.
The concept of the continuous firewall cross-member is also new in the CL-Class. During an offset frontal crash, this widely distributes the impact forces into the transmission tunnel and the side members. An additional, upper member increases the rigidity of the firewall and reduces pedal intrusion into the interior in the event of a frontal impact.
The V-engines of the CL-Class make a further, important contribution to occupant protection. Thanks to their compact construction, they allow a higher deformation of the front-end structure during a frontal impact, reducing the loads acting on the passengers. The propshaft is also equipped with special deformation elements.
Distributing impact forces over several vertical and horizontal structures with specifically defined energy levels not only benefits occupant protection, but also serves the interests of compatibility during collisions with smaller vehicles. The front-end structure of the new CL-Class is designed to ensure that crash energy is also dissipated for the other vehicle.
Robust floor structure with eight longitudinal members
Whether during a frontal or rear-end crash, lateral impact or rollover, the passenger cell is an extremely robust structure which is able to offer the occupants an intact survival space even at high impact speeds. High-strength steels and thicker steel panels play an important part in this, as does the installation of additional structural members.
An intelligently designed floor structure forms the robust basis for effective occupant protection: eight longitudinal members, four cross-members and triple tunnel reinforcement stabilise the passenger cell during a crash, and ensure that the impact forces are distributed over a wide area.
Side structure of higher-strength steel
During a side impact, the robust side members, the B-pillars, the four cross-members at floor level and a solid steel section below the dashboard are responsible for the stability of the passenger cell. For the first time Mercedes-Benz has used higher-strength steel alloys for the side members and B-pillars. In terms of tensile strength these are far superior to any other material. Side impact protection is also the purpose of the high-tensile reinforcing sections of aluminium integrated into the doors. Mercedes engineers also devoted particular attention to the door hinges, for which they developed special, high-strength mounting plates. This creates a robust, integrated structure which is able to provide effective protection to the occupants in the event of a lateral collision.
Rear-end structure designed to withstand extreme impact loads
As for frontal and side impacts, the new CL-Class meets the most stringent safety standards where a rear-end impact is concerned, for example the new US legislation which prescribes an offset crash (70 percent overlap) with an impact speed of 80 km/h.
The fact that the passenger cell remains substantially undamaged despite this extremely high load is due to the sophisticated deformation zone at the rear. In addition to an aluminium cross-member and the steel crash boxes of the bolt-on rear-end module, this consists of two robust side members and a cross-member in the area of the boot floor. The rear axle subframe also forms an energy-absorbing level during an impact. The fuel tank is located in a protected area in front of the rear axle.
Restraint systems: activation according to accident severity
During a crash, an effective restraint system goes into action to protect the vehicle occupants as the situation requires. To this end a computer not only uses various sensors to evaluate the severity of an impact, but also the personal data of the front passenger. If the sensors in the seat cushion identify the front passenger as small, then depending on the type of accident, they initially only activate the first airbag stage for less than maximum inflation. If a larger front passenger is detected, both airbag stages are activated. The well-proven automatic child seat recognition system is also on board. This deactivates the front passenger airbag as soon as a rear-facing child seat with a transponder is detected. The airbag, sidebag and belt tensioner are deactivated when the front passenger seat is unoccupied.
The engineers in Sindelfingen have also made further improvements to the sensor systems. The new CL-Class has a total of eleven sensors which supply information about the type and severity of an impact at an early stage:
- Frontal impact: In addition to the central sensor in the airbag control unit, the CL-Class is equipped with so-called up-front sensors. By virtue of their exposed position on the front-end module, these are able to detect the severity of a collision even earlier and with greater accuracy, which enables the time between the crash and activation of the airbags and belt tensioners to be reduced even further. The belts can therefore be tensioned at a very early stage, so that the occupants are connected to the passenger cell during an impact and benefit from the deceleration of the body structure.
Side impact: New pressure sensors rapidly and reliably inform the control unit when a lateral impact occurs in the door area. These sensors respond when the air between the outer skin and the interior panel of the door is compressed by an impact. Additional side sensors are installed in the B-pillars of the new CL-Class.
Rear-end collision: The central crash sensor in the interior of the new CL-Class recognises a rear-end collision. If the impact is severe, the belt buckle tensioners in the front and rear are activated to hold the occupants more firmly in their seats.
Rollover: In the event of a rollover, a rollover sensor integrated into the airbag control unit is able to activate the belt tensioners, and if necessary the windowbags.
Belt tensioner and belt force limiter for every seat
In addition to the two-stage front airbags for the driver and front passenger, the standard occupant protection system in the new CL-Class includes a total of six side protection airbags: two sidebags in the front seat backrests, two sidebags in the rear side panels and two large windowbags.
All the occupants have the benefit of three-point inertia-reel seat belts with belt tensioners and belt force limiters. The loads acting on the occupants are also reduced by the newly developed steering column, which collapses telescopically by up to 80 millimetres during a frontal collision.
Mercedes safety even after an accident
The comprehensive Mercedes safety concept PRO-SAFE also takes the post-accident phase into consideration. In order to prevent consequential damage, the fuel supply to the engine is automatically interrupted if the new CL-Class is involved in an accident of sufficient severity. The hazard warning system is also switched on to warn following traffic and prevent further accidents.
After an accident with airbag activation, all the side windows are opened very slightly to ventilate the interior. The door locks are also automatically unlocked so that helpers are able to recover injured passengers more rapidly. Specially designed crash joins prevent the doors from being jammed shut by the wings. The occupants are also able to open the doors after an accident, as Mercedes-Benz uses Bowden cables, which remain intact after deformation, to operate the door catches from the inside. Like the S-Class, the new CL-Class has markings on the rear windscreen which indicate the points where the emergency services should cut through the C-pillars after a serious accident, in order to reach the occupants rapidly for medical treatment.