Active safety: Radar, cameras and sensors - New assistance systems for safe motoring

Apr 22, 2009
  • Standard-fit ATTENTION ASSIST warns against drowsiness in plenty
    of time
  • Adaptive Highbeam Assist selects the optimum light settings automatically
  • Speed Limit Assist displays the currently permitted speed in the cockpit
  • DISTRONIC PLUS offers proximity control and Brake Assist PLUS
  • Autonomous emergency braking if there is an acute risk of an accident
  • Outstanding aerodynamics enhance active and perceptual safety
Preventing traffic accidents is at the heart of Mercedes-Benz's commitment to safety. This is why the engineers in Sindelfingen are dedicated to advancing the development of sophisticated assistance systems which warn and assist the driver in critical situations and can act autonomously if there is acute danger. ABS, ESP® and Brake Assist were the first technologies of this kind; their positive effect has since been confirmed by accident statistics.
The new or modified driver assistance systems in the E-Class Coupé are based
on state-of-the-art radar, camera and sensor technology. They are specially configured to help reduce the number of accidents caused by being too close to the vehicle in front, drowsiness and darkness.
ATTENTION ASSIST, invented by Mercedes, is specified as standard. With this system, Mercedes-Benz is making a further key contribution towards active safety as, according to studies, around a quarter of all serious motorway accidents are caused by drowsy drivers - making drowsiness an even bigger cause of accidents than drink-driving. The drowsiness-detection system monitors the driver's behaviour on a permanent basis, recording a total of more than 70 parameters to gauge the driver's level of awareness. This continuous monitoring is crucial for detecting the floating transition from awakeness to drowsiness and for giving the driver plenty of warning.
Based on this wealth of data (see figure), ATTENTION ASSIST calculates an individual driver profile during the first few minutes of every trip. This profile is then compared with the current sensor data and the prevailing driving situation by the car's electronic control unit. In addition to the vehicle speed, lateral acceleration and longitudinal acceleration, the Mercedes system also detects use of the turn indicators and the pedals as well as certain control inputs and external influences such as side winds or road unevenness, for example.
Drowsiness detection: steering behaviour as the key indicator
Four years of development and testing work on the ATTENTION ASSIST system revealed steering behaviour to be an extremely meaningful indicator of drowsiness. In the tests involving over 670 drivers, the Mercedes scientists determined that drowsy drivers have trouble steering a precise course in their lane, making minor steering errorsthat are often corrected quickly and abruptly. This effect occurs at an early stage when drowsiness kicks in - often before the dangerous microsleep phase. ATTENTION ASSIST is active at speeds of between 80 and 180 km/h.
If the system detects drowsiness, it emits an audible warning signal and flashes up an unequivocal message on the display in the instrument cluster:
Highbeam Assist: optimum light distribution in every driving situation
Driving can be particularly dangerous at night. Although there is far less traffic on the road in the evening and at night, almost 40 percent of all fatal traffic accidents occur during the hours of darkness. One of the main causes of accidents is the driver's lack of visibility. According to a study carried out by the TÜV (German technical inspection authorities), around 23,000 serious accidents involving 1200 deaths could be avoided if all cars were fitted with powerful bi-xenon headlamps.
Mercedes-Benz has used this headlamp technology since as far back as 1999. Now the Stuttgart-based brand is unveiling a further innovation in the shape of optionally available Adaptive Highbeam Assist. This innovative system adjusts the range of the headlamps automatically based on the distance to oncoming vehicles or moving vehicles in front of the car with their lights on. Consequently, the best possible headlamp range is always selected, allowing the driver to see the course of the road, pedestrians or danger spots more clearly and at an earlier stage. The low-beam range can therefore be increased from around 65 to up to 300 metres - without dazzling other motorists.
This innovative 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 a special 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 and controlling the beam of light so that it always ends in front of the other vehicles.
Adaptive Highbeam Assist additionally takes into account the steering angle in order to dim the headlamps on tight bends. If the road ahead is clear, the system performs a gradual transition to high-beam mode.
Realistic tests confirm that motorists who use Adaptive Highbeam Assist are safer on the road in the dark: dummies placed at the side of the road to simulate pedestrians were detected from a distance of around 260 metres - around 150 metres earlier than is the case when conventional low beam is used - despite the presence of oncoming traffic. The new Mercedes assistance system therefore offers more than double the safety at night. What's more, the system helps to relieve driver stress as there is no longer any need to repeatedly flick the stalk on the steering wheel. So the driver can concentrate more on actually driving the car.
Adaptive Highbeam Assist is ready to act 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 wheel.
Intelligent Light System: five light functions with bi-xenon headlamps
The Intelligent Light System is another innovation in lighting technology available for the new E-Class Coupé. This optional extra provides five different light functions designed specifically for typical driving situations and weather conditions:
  • The familiar low-beam headlamps are replaced by country mode, which illuminates the road verge on the driver’s side more broadly and brightly than before. This enables drivers to orientate themselves even more easily in the dark, and respond more rapidly when other road users cross the road.
  • Motorway mode, which comes on automatically when driving above 90 km/h, increases the driver's range of vision by up to 60 per cent. This lighting function is activated in two stages: the Intelligent Light System first increases the output of the bi-xenon bulbs 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 is triggered at 110 km/h, when the beam of the bi-xenon module on the driver’s side is elevated slightly. 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.
  • With the enhanced fog lamps, 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 fog lamp 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.
  • Depending on the steering angle, yaw rate and vehicle speed, the active light function pivots the headlamps sideways by up to 15 degrees in fractions of a second to greatly improve road illumination. On a long sweeping bend with a radius of 190 metres, the driver is able to see 25 metres further than with conventional low-beam headlamps thanks to the active light function, which, incidentally, operates with both low and high beam.
  • The cornering light function improves safety at crossroads, at T-junctions and on tight bends. It is activated automatically when the driver turns the steering wheel at a speed below 70 km/h. The lights 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 up to 65 degrees.
The new E-Class Coupé is fitted with halogen headlamps as standard. For low beam, the Mercedes engineers have developed a sophisticated projection system, which is housed in the two larger lamps at the front end. The inner headlamps, based on reflection technology, provide the high beam and serve as side lights. Headlamp Assist, which switches on the headlamps automatically when it is raining, at dusk/dawn, in the dark and when entering a tunnel, is likewise specified as standard.
When it comes to road safety, being seen is as just as important as seeing - and not just at night. This is why the standard equipment package for the E-Class Coupé includes circular daytime driving lights based on halogen technology, which are located next to the likewise standard-fitted fog lamps and switch on automatically when the engine is started. They are deactivated when the driver switches on low beam. If the Intelligent Light System (optional) is specified, the daytime driving lights are formed by a total of 14 light emitting diodes (LEDs) arranged in an L-shape, which offer high light output but have a low energy consumption of just ten watts. These are dimmed when low beam is switched on. In this case, the fog lamps are integrated in the main headlamps.
Tail lights: LEDs for every function
Mercedes-Benz also specifies LEDs as standard for the indicators, tail lights,
brake lights and rear fog light in the rear light clusters. One of the advantages of LEDs is their quick response, meaning that drivers behind receive an earlier warning if the Coupé's brakes are applied in the event of danger. What's more, this technology allows a new and unmistakable night design.
Like many of the latest Mercedes passenger cars, the new Mercedes Coupé is fitted with adaptive brake lights, which flash four times as fast as the hazard warning lights during an emergency stop and, therefore, provide an extremely effective warning for drivers behind if a head-to-tail collision is imminent.
The combination of directly and indirectly emitting LEDs used for the tail lights ensures that the red sections of the rear light clusters, which are drawn deeply into the car's flanks, are illuminated homogeneously.
Speed Limit Assist: speed limit displayed in the instrument cluster
As well as being used by Adaptive Highbeam Assist, the electronic camera located on the inside of the windscreen provides the image information for Speed Limit Assist (optional). This newly developed system reminds drivers of the speed limit currently in force by displaying it in the instrument cluster - a further contribution towards preventing accidents.
The image recorded by the windscreen-mounted camera is scanned for round surfaces only by an electronic control unit. These surfaces are then highlighted. In the next step, an algorithm 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 sent to the cockpit display, where they remain visible until the speed restriction is lifted or changed. The driver is therefore always aware of the current speed limit and can adjust the car's speed accordingly.
Thanks to the huge strides forward 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 practically instantaneously. Plus it makes no difference whether the speed-limit sign is at the side of the road or on a gantry above the road. The system is therefore able to react to variable speed limits (often indicated on gantries) as well as temporarily erected speed-limit signs, for example at road works.
Some of the speed-limit signs in Europe - for example those seen when entering or leaving towns in certain countries - are rectangular. 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 when the car enters a built-up area, for example.
DISTRONIC PLUS: radar systems to help prevent head-to-tail collisions
Radar - for monitoring events in front of and behind the car as well as warning the driver in critical situations - is a tried-and-trusted technology introduced at Mercedes-Benz in 1998. It plays an important part in helping to prevent accidents, as shown by an analysis based on representative accident-research data. This technology can prevent a fifth of all head-to-tail crashes in Germany alone. On motorways, the accident rate can be reduced by as much as around 36 percent. For the new E-Class Coupé, Mercedes-Benz offers a radar-based assistance system in the shape of DISTRONIC PLUS (optional), which also incorporates Brake Assist PLUS.
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.
This technology helps the driver to gauge the level of risk and, in combination with Brake Assist PLUS, makes the calculated brake boosting force available instantly, even if the driver does not press the brake pedal forcefully enough. Brake Assist PLUS allows controlled, targeted braking and, if necessary, increases the braking force right up to the point at which an emergency stop is performed, depending on the road speed and the distance to the vehicle in front.
When a potential accident situation is recognised, two wide-angle short-range sensors with an 80-degree beam width and a range of around 30 metres, located behind the front bumper, and a long-range radar with a range of 200 metres, located in the radiator grille, are called upon to offer assistance. In addition, the sensor system now also has medium-range detection capability, allowing monitoring of the area up to around 60 metres ahead of the car with a 60-degree beam width. This new technology enables even more accurate monitoring of the traffic situation and even better detection of dynamic events such as a car in front swerving suddenly.
PRE-SAFE® Brake: autonomous braking as "electronic crumple zone"
Accident research shows that drivers do not always react as quickly as necessary at critical moments - for example because they are distracted and therefore do not recognise the immediate danger of a head-to-tail collision, or because they fail to heed the warning signals given by an assistance system. The PRE-SAFE® Brake intervenes in situations such as these by braking the car automatically. It does so in 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 4 m/s²) as well as activating the reversible PRE-SAFE® occupant protection systems as a precaution.
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 maximum braking force is made available or, if the driver swerves, the accident can be avoided at the last moment, depending on the driving situation.
If the driver fails to react, however, even after automatic partial braking, the PRE‑SAFE®Brake activates the maximum braking power around 0.6 seconds
before the now unavoidable collision. This emergency braking can reduce the severity of the impact by a substantial margin.
Effect: impact speed reduced by 16 km/h on average
Realistic tests carried out by the Mercedes engineers have revealed that autonomous PRE-SAFE® braking reduces the impact speed by 16 km/h on average. The system therefore acts like an "electronic crumple zone", offering the car occupants an even higher level of protection.
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.
Parking aid: ultrasonic measurement of parking spaces
A newly developed system that can help drivers 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. After reverse gear has been engaged, instructions for safe parking appear on the display in the instrument cluster.
The tried-and-trusted Mercedes PARKTRONIC system (optional extra), which uses LEDs and audible signals to indicate the distance between the Coupé and an obstacle or another vehicle when parking, is integrated in the Parking Guidance system.
Mercedes‑Benz offers a further parking and manoeuvring aid in the shape of a reversing camera which films the area behind the E-Class Coupé and sends the image to the display in the centre of the dashboard.
The driver assistance systems for the new E-Class Coupé at a glance:
Standard: ensures that the car remains steerable, even when braking.
Standard: reduces the risk of skidding and stabilises the car.
Brake Assist
Standard: provides full braking power almost instantaneously in the event of an emergency stop.
Adaptive brake lights
Standard: the brake lights flash to warn drivers behind if the brakes are applied in an emergency.
Standard: detects driver drowsiness by means of sensor signals and warns the driver.
Intelligent Light System
Optional: incorporates five light functions specially configured for typical driving situations and weather conditions.
Adaptive Highbeam Assist
Optional: detects vehicles in front or oncoming vehicles and, in each case, provides the optimum headlamp range (available from the fourth quarter of 2009).
Optional: uses radar to automatically maintain a desired distance between the E-Class and the vehicle in front and warns the driver if the gap narrows rapidly.
Brake Assist PLUS (part of DISTRONIC PLUS)
Optional: uses radar sensors to detect an imminent head-to-tail collision, calculates the level of braking assistance required and provides this assistance instantaneously when the brake pedal is pressed.
Optional: initiates partial or emergency braking automatically if there is an acute risk of an accident and the driver fails to react.
Speed Limit Assist
Optional: uses a camera to detect speed-limit signs and indicates the current speed limit on the display (available from the fourth quarter of 2009).
Parking aid
Optional: ultrasonic sensors measure the length of parking spaces as the car drives past; instructions for safe parking appear on the display.
Aerodynamics: best cd figure of all series-production cars
Like its Saloon counterpart, the new E-Class Coupé is exceptionally aerodynamic – one of the main reasons behind the high level of active safety and the low fuel consumption. The drag coefficient (cd figure) is as low as 0.24, depending on model, which is around eleven percent lower than the figure for the previous model, making the new E-Class Coupé the world's most aerodynamic series-production car. The exact figures:
New E-Class Coupé
Preceding model
Drag coefficient (cd)
Frontal area (A) m²
Wind resistance (cd x A) m²
*For E 220 CDIBlueEFFICIENCY Coupé, available from spring 2010
The rear of a car affects the drag coefficient even more than the front section, since the air swirl that can occur here acts like an invisible brake and increases fuel consumption unnecessarily. One of the ways in which the Mercedes experts prevent such air swirl is by incorporating a discreet, barely visible spoiler lip in the central area of the boot lid. In addition to this, they equip the tail-light lenses with special spoiler lips, which direct the airstream flowing along the car's flanks a long way rearwards; were these small spoiler lips not included, the air would flow inwards at the rear of the Coupé and create a vacuum, which would have a negative impact on both wind resistance and lift.
Further aerodynamically effective details displayed by the new E-Class include:
  • Controllable fan shutter: allows the amount of cooling air to be limited as required, depending on the driving situation. Otherwise heavy pressure losses would occur as the air made its way into the engine compartment.
  • Sealed joints between the bonnet and headlamps: ensure an even better airflow around the front section.
  • Wheel spoilers on the front and rear wheels: improve the airflow around the tyres and reduce lift.
  • Cladding of the engine compartment and the underbody: optimises the flow of cooling air from the engine compartment and prevents flow losses caused by air blockage und swirl on the underbody.
  • Aerodynamic exterior mirror housings: improve aerodynamics as well as aeroacoustics and safety.
The exterior mirrors also play a crucial role in enhancing perceptual safety as they improve the driver's visibility in the rain. The mirror housings are designed so that any rainwater hitting them flows outwards in a narrow groove running around the outside so that it can drip off at a precisely defined point. As a consequence, the side windows remain largely clean, affording the driver an unimpeded view of the exterior mirror and the outside. The A-pillars likewise help to keep dirt away from the side windows as they feature special water guides where the rainwater hitting the windscreen is collected before being blown downwards as well as rearwards across the roof by the airflow.