Following a successful commitment to occupant protection, the future focus of the developers at Mercedes-Benz will be more and more on the prevention of traffic accidents and the mitigation of their severity. The approach of the safety specialists in Sindelfingenfollows the principle of “Real Life Safety”.
The majority of all the safety measures are based on findings from accident research, and are a response to what actually happens during accidents. Examples include well-proven Mercedes inventions such as ABS, ESP®, Brake Assist and PRE-SAFE®. The development aim in these cases was to prevent particularly frequent and serious accidents, or at least – if an accident does occur – to mitigate the effects.
In the 2009 S-Class, Mercedes-Benz has continued this successful strategy with a pioneering synergy of the very latest assistance systems which turn the luxury saloon into an “intelligent” partner that can “see”, “feel” and act independently. In line with this concept the new Mercedes-Benz model not only protects its occupants, but can also contribute decisively to the safety of other road users.
In addition to radar sensors, Mercedes-Benz also uses cameras for the first time in the S-Class – these are able to look well ahead and monitor the car’s surroundings. The system’s processors are in turn able to interpret critical situations on the basis of this information. The new camera-based assistance systems e.g. help the driver to stay in his lane, recognise speed limit signs, control the headlamps as the situation requires and provide enhanced visibility in the dark.
The right light in any driving situation with the Intelligent Light System
The Intelligent Light System (standard for S 400 HYBRID and S 600) offers five different bi-xenon light functions, each of which is suited to typical driving or weather conditions:
– Country mode
– Motorway mode
– Enhanced foglamps
– Active light function
– Cornering light function
The light system is based on powerful bi-xenon headlamps. These are variably controllable, and are networked with other electronic control units from which the headlamps obtain information about the current driving situation and distribute their beam patterns accordingly. The familiar low-beam headlamps are replaced by the new country mode, which illuminates the road verge on the driver’s side 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 the vehicle’s path.
Motorway mode is activated automatically from a speed of 90 km/h, increasing the visibility range 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 headlamps from 35 to 38 Watts, thereby increasing the light intensity with noticeably better illumination of the carriageway and its verges.
The second stage is activated from 110 km/h, when the bi-xenon module on the driver’s side is raised slightly. The beam range in motorway mode is around 120 metres; at the centre of the cone of light the driver is able to see around 50 metres further than with the previous dipped beams.
Motorway mode increases visibility by 60 percent
With the enhanced foglamps, Mercedes-Benz improves driver orientation when visibility is poor. The new lighting function is activated at speeds below 70 km/h, as soon as the rear foglamp is switched on. The variable headlamp technology incorporated in the Intelligent Light System makes it possible to pivot the bi‑xenon headlamp on the driver’s side outwards by eight degrees, while lowering the beam of light at the same time. This adjustment illuminates the inner half of the road more brightly and reduces the degree of glare from light reflected back by the fog.
The Intelligent Light System also includes the active light and cornering light functions. These are switched on automatically: depending on the steering angle, yaw rate and vehicle speed, the active headlamps pivot sideways by up to 15 degrees in fractions of a second, thereby greatly improving road illumination. On an extended 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 in both low-beam and high-beam mode.
The cornering light function improves safety at crossroads, at T-junctions and on tight bends. It is activated automatically when the driver operates the turn indicators or turns the steering wheel at a speed below 40 km/h. The foglamps then swivel to illuminate the area diagonally in front of the vehicle for a distance of around 30 metres, with an angle of coverage of 65 degrees.
Mercedes-Benz combines the Intelligent Light System and Adaptive Highbeam Assist with daytime driving lights as well as indicators and side lights employing LED technology to form the LED Light package (standard for S 400 HYBRID and S 600).
Adaptive Highbeam Assist for the best possible road illumination
As part of the LED Light package, Mercedes-Benz combines the Intelligent Light System with Adaptive Highbeam Assist (standard for S 400 HYBRID and S 600). This recognises oncoming vehicles or vehicles ahead with their lights on, and dips the headlamps. It also adjusts the beam range of the headlamps to give the driver the best possible visibility – without dazzling oncoming road users. The driver is able to see the course of the road, pedestrians and potential hazards more easily, and respond at an earlier stage.
Once the system registers oncoming vehicles or vehicles ahead with their lights on, it continuously adjusts the beam range to the distance so that the cone of light ends before it meets these vehicles. Adaptive Highbeam Assist also takes the steering angle into account, dipping the headlamps on tight bends. On clear stretches of road the system smoothly switches over to main beam. Practical trials have shown that drivers travel in greater safety in the dark with Adaptive Highbeam Assist: despite oncoming traffic, dummy pedestrians positioned at the roadside were also detected at a range of around 260 metres — about 150 metres sooner than with conventional dipped headlamps. This new Mercedes assistance system therefore more than doubles the safety margin when driving at night. Adaptive Highbeam Assist gives the best possible visibility without dazzling other drivers.
The system also relieves driver workload: he is no longer required to operate the multifunction stalk on the steering column, and can devote more attention to the road ahead. Once activated, Adaptive Highbeam Assist always ensures the best possible headlamp beam range. Research has shown that at night, the main beams are only switched on during around eight percent of all journeys.
Data transfer every 40 milliseconds
The newly developed Mercedes technology is based on a camera located on the inside of the windscreen, which monitors the traffic situation in front of the car. Thanks to an intelligent image-processing algorithm, the camera is able to detect other vehicles and the distance to them. The range of the variable-control bi-xenon headlamps is set based on these findings and adapted continuously depending on the distance to the vehicle in front or the oncoming traffic. The system operates at lightning speed, sending new data to the headlamps every 40 milliseconds.
Adaptive Highbeam Assist is ready to respond at speeds above 55 km/h, and operates autonomously once the driver has moved the rotary light switch to the “Auto” position and selected high beam using the multifunction stalk on the steering column.
Night View Assist PLUS with new function for highlighting pedestrians on the display
The Night View Assist Plus system likewise available for the S-Class uses infrared technology to enhance the driver’s range of vision when the main beams cannot be used: two separate headlamps illuminate the road with invisible, non-dazzling infrared light. A windscreen-mounted camera designed to pick up precisely this type of light records what happens in front of the car and sends the image to a display in the instrument cluster. The clear, needle-sharp greyscale image that appears here shows the scene in front of the car, allowing the driver to see pedestrians, cyclists or obstacles on the road at an early stage. Night View Assist Plus features special pedestrian detection.
The latest development stage of the Night View Assist features special a special pedestrian-detection function: as soon as the system detects pedestrians ahead of the car, they are highlighted on the display to make it easier for the driver to see them.
Lane Keeping Assist gives a warning if the vehicles leaves its lane unintentionally
As a further system that “looks ahead”, the newly developed Lane Keeping Assist is available for the 2009 S-Class. Vehicles leaving the road unintentionally is the cause of one in six serious accidents on German roads. More than one third of all traffic fatalities are victims of such accidents.
The centrepiece of this new technology is a camera on the inside of the windscreen, which is able to recognise clear lane markings by evaluating the contrasting images of the road surface and the markings. The image processing system informs an electronic control unit, which determines the position of the vehicle and recognises when the vehicle leaves its lane to the right or left unintentionally. Unlike conventional systems of this kind, the Mercedes system is able to evaluate the driver’s activities as well, and can reliably ascertain whether the car is leaving its lane intentionally or not. There is therefore no warning if the driver e.g. accelerates before overtaking or joining a motorway, brakes heavily or enters a bend.
If the system determines that the car is leaving its lane unintentionally, it activates an electric motor, causing the steering wheel to vibrate – a discreet yet highly effective way of prompting the driver to countersteer. The timing of the warning depends on the width of the road and the type of lane markings. If the car crosses over a continuous line on the road, as opposed to a broken one, the system emits its warning earlier.
Lane Keeping Assist operates at speeds of between 60 and 250 km/h, as soon as the system has detected a lane marking. The steering wheel does not vibrate to give a warning if the driver …
– cuts a corner intentionally
– uses the turn indicators
– moves back into the original lane after overtaking
Furthermore, Lane Keeping Assist is deactivated immediately if ABS, ESP®,Brake Assist or another safety system intervenes.
Electronic image processing system recognises speed-limit signs
Intelligent electronic image processing is also the basis for the likewise newly developed Speed Limit Assist, which is available as part of the Navigation package as an optional extra for the 2009 S-Class (standard for S 400 HYBRID and S 600). This new Mercedes assistance system reminds the driver of a speed limit it has recognised. The applicable speed limit is shown in a display in the instrument cluster, and remains visible until no speed limit applies or a different speed limit is registered – an important contribution to safety, as unsuitable speeds are the cause of the most and most serious accidents worldwide. Traffic signs indicating the speed limit appear in the instrument cluster.
A windscreen-mounted camera monitors the area in front of the car on a permanent basis, and literally has a trained eye for road signs showing speed limits. This is because a computer scans the camera image for round surfaces only and then highlights these. As a next step, a system of algorithms filters out all objects that are round but do not resemble traffic signs. Finally, a comparison with stored patterns eliminates all but those objects which the system is programmed to detect: round traffic signs indicating the speed limit. The symbols are displayed in the instrument cluster, meaning that the driver is always aware of the current speed limit and can adjust the car’s speed accordingly.
Some of the speed-limit signs in Europe – for example those seen when entering or leaving towns – are rectangular, however. In such cases, the assistance system also scans the data stored on the navigation system’s digital map to check the plausibility of the camera image. The last speed limit detected disappears from the display in the instrument cluster as soon as the car enters a built-up area, for example.
Thanks to the huge advances made in computer-based image-processing technology, Speed Limit Assist is able to work in real time, analysing the images within a fraction of a second so as to provide the driver with the required information very rapidly. It also makes no difference whether the speed-limit sign is at the side of the road or on a gantry above the road.
ATTENTION ASSIST is able to warn the driver before potentially fatal micro-sleep occurs
The attention of Mercedes-Benz accident researchers is also directed towards the dangers of micro-sleep at the wheel. Scientific studies have concluded that around 25 percent of all serious motorway accidents are caused by drowsy drivers. Accordingly this accident cause is even more significant than drinking and driving. The ATTENTION ASSIST system installed in the 2009 S-Class as standard* is able to recognise the typical signs of drowsiness and warn the driver early on that it is time to take a break.
*Not for S 400 HYBRID
The risk of falling asleep momentarily is at its greatest on long-distance journeys in the dark or in unchanging conditions because this is when drivers are most likely to suffer a lapse in attention. The sheer monotony further heightens the risk of falling asleep at the wheel. Studies show that, after just four hours of non-stop driving, reaction times can be up to 50 percent slower. So the risk of an accident doubles during this time. And the risk increases more than eight-fold after just six hours of non-stop driving!
ATTENTION ASSIST observes the driver’s behaviour and, at the start of every trip, produces an individual driver profile that is then continuously compared with current sensor data. This permanent form of monitoring is important for detecting the floating transition from awakeness to drowsiness and for warning the driver in plenty of time. The system is active at speeds of between 80 and 180 km/h.
Steering behaviour as the key indicator of drowsiness
As well as the speed, lateral acceleration and longitudinal acceleration, the Mercedes system detects steering wheel movements, use of the turn indicators or pedals and certain control inputs, and takes into account external influences such as crosswinds or road unevenness, for example. ATTENTION ASSIST monitors more than 70 different parameters. Observation of steering behaviour has proven to be extremely meaningful, as drowsy drivers find it difficult to steer a precise course in their lane and show a characteristic steering behaviour pattern. Intensive tests carried out by Mercedes engineers, involving more than 550 drivers, show that this effect occurs at a very early stage when drowsiness kicks in – often before the dangerous situation in which the driver falls asleep momentarily (microsleep phase).The crucial element of the Mercedes system is a high-resolution sensor which enables precise monitoring of steering movements and steering speed. Based on these data, ATTENTION ASSIST calculates an individual behavioural pattern during the first few minutes of every trip. This pattern is then continuously compared with the current steering behaviour and the current driving situation, courtesy of the vehicle’s electronic control unit. This process allows the system to detect typical indicators of drowsiness and warn the driver by emitting an audible signal and flashing up an unequivocal instruction on the display in the instrument cluster: “ATTENTION ASSIST. Break!”
Blind Spot Assist: radar sensors warn against dangerous lane-changes
In addition to the latest camera and image processing technology, innovative radar technology makes a major contribution to accident prevention in the 2009 S-Class. Blind Spot Assist is a prime example: first introduced in the S-Class in 2007, this system warns the driver once is recognises that a lane-change is too dangerous. In Germany alone, more than 9500 serious accidents occur each year because drivers change lanes without taking following traffic into account, or make mistakes when returning to their lane.
The Blind Spot Assist detects the area immediately adjacent to and behind the vehicle with the aid of radars.
This Mercedes system available for the S-Class as part of the Driving Assistance package can help drivers to change lanes safely: short-range radar sensors housed on both sides of the rear bumper monitor the areas directly alongside and behind the car. This process enables them to see if there is another vehicle in the next lane – in the so-called blind spot. In such situations, the system informs the driver by illuminating a red warning symbol in the lens of the exterior mirror. If the driver fails to see this warning and indicates to change lanes, a warning signal sounds as well.
DISTRONIC PLUS: keeping a safe distance with the help of radar
DISTRONIC PLUS proximity control and Brake Assist (BAS) PLUSare two more radar-based Mercedes-Benz assistance systems available for the S-Class. An analysis by Mercedes-Benz accident researchers has shown that an average of one fifth of all rear-end collisions could be prevented with this technology in Germany alone. In a further one quarter of these cases, the systems can significantly help to mitigate the severity of the accident. Interaction between radar and brake technology has the greatest safety potential of all on motorways, where around 36 percent of all rear-end collisions could be prevented.
DISTRONIC PLUSproximity control operates at speeds of between 0 and 200 km/h: it keeps the car a set distance behind the vehicle in front, applies the brakes as required and can even bring the car to a complete halt, depending on the traffic situation. If the gap to the vehicle in front narrows too quickly, the system gives the driver an audible warning and, as soon as this first warning signal sounds, automatically calculates the brake pressure required to prevent a collision in this situation. DISTRONIC PLUS is part of the Driving Assistance package.
Brake Assist (BAS) PLUS “looks ahead”
Brake Assist (BAS) PLUS detects the distance to vehicles in front and in the event of an impending rear-end collision calculates the necessary degree of braking assistance. If the driver does then in fact apply the brakes, either because traffic is building up or he has been warned by the PRE-SAFE® Brake, in fractions of a second the new Brake Assist (BAS) PLUS builds up the brake pressure calculated for the current situation and – if necessary – increases brake pressure up to full brake application.
DISTRONIC PLUS and Brake Assist (BAS) PLUS celebrated their world premiere in the S-Class in 2005. For the 2009 S-Class, Mercedes-Benz has improved this innovative radar technology even further.
Situations potentially leading to an accident are recognised by two short-range radar sensors behind the front bumper (80-degree scanning angle), which have a range of around 30 metres, and a long-range radar sensor in the radiator grille. Mercedes-Benz has improved the performance of these sensors even further. In the 2009 S-Class, the system uses a newly developed long-range radar sensor with a range of 200 rather then the previous 150 metres.
This sensor now also allows mid-range detection, monitoring the area up to 60 metres ahead of the car with a scanning angle of 60 degrees. This new technology enables the road ahead to be monitored even more precisely, with better detection of dynamic processes such as a sudden lane-change by a vehicle ahead.
PRE-SAFE® Brake acts as an “electronic crumple zone”
If the driver is distracted, and fails to heed the immediate danger of a rear-end collision and ignores the visual and acoustic warnings, the PRE-SAFE® Brake is able to intervene and brake the vehicle autonomously.
This process has two stages:
Around 1.6 seconds before the calculated impact point – after three audible warning signals – the system initiates partial braking autonomously and decelerates the car with around 40 percent of the maximum braking power (approx four m/s²). Designed to supplement the visual and audible warnings, autonomous partial braking gives the driver a further, perceptible signal to act. If the driver then brakes immediately, the adapted braking force is made available by the Brake Assist (BAS) PLUS. If the driver swerves, the accident can be avoided at the last moment.
The 2009 S-Class makes use of the latest development stage of the PRE-SAFE® Brake: if the driver fails to react even after this autonomous partial braking, it is able to activate the maximum braking pressure in this second stage in around 0.6 seconds before what is now recognised as an unavoidable accident — an emergency braking action that can significantly mitigate the severity of the impact. The PRE-SAFE® Brake therefore acts as something like an “electronic crumple zone” to give the occupants even greater protection.
Die PRE – SAFE ® Brake uses the same close-range and long-range radar sensors as DISTRONIC PLUS and Brake Assist ( BAS ) PLUS . Mercedes-Benz offers all three systems in combination as part of the Driving Assistance package. In Germany around 40 percent of S-Class customers equip their car with this safety technology.
The PRE-SAFE® Brake greatly reduces the severity of accidents
Mercedes-Benz has tested the functioning and effectiveness of the PRE-SAFE® Brake in practical trials and in the driving simulator. The practical trials involved around 400 drivers in Germany and the USA, who covered a total of around one million test kilometres. Mercedes engineers also conducted a series of tests lasting several weeks and involving 70 drivers in the driving simulator at the Daimler research facility in Berlin. Each of the drivers drove for half an hour and was distracted by an accident on the other side of the road, while at the same time the traffic in front of the car braked suddenly.
The results of the test, which reflects an everyday situation on the road, highlight the safety-enhancing effect of the sophisticated assistance systems: a total of 70 percent of these test drives remained accident-free thanks to the fast reactions of the drivers and the assistance provided by Brake Assist (BAS) PLUS and the PRE-SAFE® Brake. In a third of the simulator tests, those taking part were unable to avoid a crash. In these cases, automatic braking greatly reduced the accident severity. The practical trials conducted by Mercedes engineers showed that the impact speed is reduced by an average of 16 km/h by autonomous PRE‑SAFE® braking.
The PRE-SAFE®Brake is active at speeds of between 30 and 200 km/h when moving vehicles are detected in front of the car. The system also reacts if the car approaches a stationary queue of traffic, providing the car’s speed is below 70 km/h.
Just like the airbag, seat-belt tensioner, ESP® and other trailblazing Mercedes inventions, the PRE-SAFE® Brake was developed based primarily on real accident situations. When used in combination with Brake Assist (BAS) PLUS, this technology can make a key contribution towards reducing the high number of rear-end collisions or reduce the severity of such collisions. In Germany, over 17 percent of all serious road accidents involve rear-end collisions. In the USA, one in three road accidents involving deaths or injuries are rear-end collisions.
PRE-SAFE® reduces the forces acting on occupants during accidents by up to 40 percent
The PRE-SAFE® Brake is an optional component of the preventive occupant protection system PRE-SAFE®, which is standard equipment in the Mercedes-Benz S-Class and immediately takes protective action when the system recognises the danger of an accident. This intelligent Mercedes system, which had its world premiere in the S-Class in 2002 and has been continuously improved ever since, takes its lead from Nature: just as living creatures react reflexively and seek cover when danger threatens, PRE-SAFE® activates precautionary measures for the passengers. When PRE-SAFE® e.g. detects that skidding is imminent, the driver brakes sharply or the PRE-SAFE® Brake has intervened, the system tensions the front seat belts, moves the front passenger seat into the most favourable position and automatically begins to close the side windows and sliding sunroof if appropriate. The position of the electrically adjustable, individual rear seats is also improved.
PRE – SAFE ® can also be activated if the optional Brake Assist ( BAS ) PLUShas used the radar system to predict an impending collision and a certain level of deceleration is exceeded when braking. The occupants are prepared for the potential collision by preventive tensioning of the front seat belts and repositioning of the front-passenger seat, enabling the seat belts and airbags to offer the best possible protection.
As another PRE-SAFE® measure, the optional rear multicontour seats and further developed active multicontour front seats enable the driver and front passenger to be seated even more securely, thereby limiting dangerous whiplash movements by the upper body. If the PRE-SAFE® control unit detects a critical driving situation, it instantly activates the air chambers in the seat cushions and backrests. These then envelope the seat occupants and give them support. Tests at the Mercedes-Benz Technology Center have shown that this PRE-SAFE® function and preventive belt tensioning increases the distance between the shoulder and the inner door lining by up to 40 millimetres at a lateral acceleration of 0.6 g. This enables the sidebag to fulfil its protective function even more effectively.
The aim is to prepare the occupants and the car for an imminent collision, so that the seat belts and the airbags can deploy with maximum effect in the event of an impact. What’s more, the PRE-SAFE® protective measures are reversible: if the accident is averted, the advance tensioning of the seat belts is halted automatically and the occupants are able to reset the positions of the other systems. The anticipatory occupant protection system is then ready for action again straightaway.
Early accident detection is possible because PRE-SAFE® is an intelligent synergy of active and passive safety. It is linked to Brake Assist (BAS), the Electronic Stability Program (ESP®), Brake Assist (BAS) PLUS (optional), the PRE-SAFE® Brake (optional) and the short-range sensors of the DISTRONIC PLUS (optional). The sensors of these systems detect potentially critical situations and send the relevant information to the electronic control units within a matter of milliseconds. PRE-SAFE® also uses these sensor data for anticipatory occupant protection.
In the 2009 S-Class, in combination with the improved DISTRONIC PLUS and Brake Assist (BAS) PLUS, PRE-SAFE® also uses the information provided by the short-range radar sensors in the front bumper to tension the front seat belts at the very last moment before an unavoidable collision, thus reducing the forces exerted on the driver and front passenger during the crash. This PRE-SAFE® function is literally the “last resort” in anticipatory occupant protection, since the accident occurs around 200 milliseconds later. This means that the S-Class has opened up yet another new dimension in passenger car safety.
Belt tensioning reduces the forces exerted on the occupants by up to 40 percent
Analyses performed during crash tests show just how important and effective anticipatory occupant protection can be. In the case of belt tensioning, for example, the precautionary measures mean that the driver and front passenger are held in their seats in the best possible position and so do not move forwards as much in the event of an impact, thus reducing the load exerted on the head and neck area. These tests showed that the head was subjected to around 30 per cent less stress, while the Mercedes engineers recorded a reduction of around 40 per cent in the neck area.
PARKTRONIC with Parking Guidance makes slow manoeuvring easier
A newly developed system that can help the S-Class driver to park safely works on the basis of ultrasonic technology: sideways inclined sensors on the front bumper record the length of a parking space as the car drives past it (at a speed of up to 35 km/h), and indicate on the cockpit display whether the space is large enough to park in. The space must be at least 1.3 metres longer than the car. After reverse gear has been engaged, instructions for safe parking appear on the display in the instrument cluster. Parking Guidance replaces the previous Parking Assist with radar sensors.
The well-proven Mercedes system PARKTRONIC, which indicates the distance between the S-Class and an obstacle or other vehicle by means of visual and acoustic signals when parking, is also in action to assist the driver when Parking Guidance is active. As a further parking and manoeuvring aid, Mercedes-Benz offers a reversing camera that monitors the area behind the saloon and shows it in the COMAND display on the dashboard.
Individual safety according to personal height and bodyweight
If the accident is unavoidable, a powerful restraint system goes into action to protect the occupants in a way appropriate to the need and the situation. Using various sensors, a computer evaluates not only the seriousness of the accident, but also personal data describing the front-seat passenger. If the sensor in the seat cushion has identified a small passenger, and depending on the type of accident, it initially deploys only the first airbag stage so that the air cushion is less fully inflated. If it detects a larger passenger, however, both airbag stages are deployed.
In addition, the S-Class comes with the proven automatic child seat identification feature that deactivates the front passenger seat airbag when a special Mercedes-Benz child seat with transponder has been recognized.
Eleven sensors for accident detection
The S-Class has a total of eleven installed sensors that provide immediate data on the type and seriousness of a collision:
Frontal impact: In addition to the central sensor in the airbag control unit, the S-Class is equipped with “up-front” sensors. Because of their exposed position in the front module, they detect the strength of an impact even earlier and with even more precision, so that the time between the crash and the activation of airbags and seat-belt tensioners can be reduced even further.
Side impact:pressure sensors relay rapid, precise information to the control unit in the event of an impact from the side in the area of the doors. These sensors react when the air between the doors’ outer skin and inner lining is compressed on impact. Additional side sensors are installed in the B-pillars
of the new S-Class.
Rear impact:The central crash sensor in the interior of the S-Class detects a rear-end collision and supplies the information needed to activate the NECK-PRO headrests. If the accident is relatively major, the pyrotechnical belt tensioners are triggered in the front and rear to fix the occupants in their seats.
Rollover: In side rollovers, a rollover sensor integrated into the airbag control unit can activate the seat-belt tensioners and windowbags.
Nine airbags as standard
With nine airbags fitted as standard, not to mention seat-belt tensioners, belt-force limiters and NECK-PRO crash-responsive head restraints for the driver and front passenger, the 2009 S-Class offers an even more extensive package of safety equipment than its predecessor. The airbags, which deploy in a matter of milliseconds in the event of an accident, for the first time include a kneebag for the driver plus two adaptive airbags for the driver and front passenger, two sidebags in the front-seat backrests and two large windowbags which extend from the A-pillar to the C‑pillar during a side impact. Rear sidebags can be ordered as optional extras.
Seat-belt force limiters for front and rear passengers
All the passengers have three-point automatic seat belts. The driver and front passenger seats and the outer seats in the rear are also equipped with seat-belt tensioners and belt force limiters. The force limiter of the front belt straps is adaptive: after attaining a certain maximum level of force, the force limiters switch to a lower level of force – the belts are loosened so that front passengers can plunge deeper into the airbags. This reduces the loads acting on the chest area of the occupants.
The steering column serves the same purpose. During a front-end impact, it collapses telescopically by up to 80 millimetres.
Sophisticated bodyshell design for high crash-resistance
The basis for the exemplary level of occupant protection is an intelligently designed bodyshell with large deformation zones at the front and rear ends. Around one half of all the components making up the bodyshell of the S-Class are of high or ultra high-strength high-tech steel alloys, which offer the maximum strength for the minimum weight. This is a top-class figure in passenger car engineering. The bonnet, front wings, doors, boot lid and other components are of aluminium.
The front module and the frame-type integral support, to which the engine, front axle and steering are attached, connect the front side members with the second side member plane above the wheel housings. During a frontal collision, this gives rise to two important paths along which forces and loads are transmitted, which is one of the major reasons for the exemplary passenger protection of the S-Class. Similarly, the solid, multi-layer side skirts can absorb large forces and divert the impact energy past the passenger compartment.
The continuous firewall cross member distributes the impact forces over a large area, into the centre tunnel and the longitudinal members at the sides. An additional upper member increases the rigidity of the firewall and reduces the extent to which the pedals are pushed into the passenger compartment during a front impact.
Practically undeformable: the passenger compartment
The passenger cell is a structure virtually immune to deformation which keeps the passengers’ survival space intact, even at high impact speeds, regardless of whether the collision is head-on, from the rear or from the side, or whether the vehicle rolls over. The use of high-strength steel and thicker panels plays as important a role here as the installation of additional load-bearing members.
A complex and carefully designed floor structure forms the sturdy foundation for comprehensive occupant protection. Eight side member sections, four cross members and a three-part tunnel reinforcement stabilize the passenger compartment in a crash, and ensure that impact forces are distributed over a large area.
Side structure made of ultra high-strength steel
In a side impact, the main elements that come into play to stabilize the passenger compartment are the sturdy side skirts, the B-pillars, the four cross members in the floor area and a solid steel section below the dashboard. Mercedes-Benz produces the sills and B-pillars using ultra high-strength steel alloys, which are far superior to all other materials in terms of their tensile strength. Side impact protection is also provided by steel reinforcing sections with a high tensile strength in the doors.
At the rear the passenger compartment is protected by a meticulously designed deformation zone. In addition to the aluminium transverse section and the steel crash boxes of the bolted rear module, this consists of two sturdy side members and a cross member in the area of the boot floor. The suspension sub-frame of the rear axle likewise forms an energy-absorbing plane in the event of an impact. The fuel tank is located in the protected area in front of the rear axle. Even with respect to rear-end protection, this means that the S-Class meets the world’s most stringent crash test standards such as the US test according to FMVSS301 at 80 km/h.
Source: Daimler AG