The new Mercedes-Benz A-Class: The driving assistance systems - Radar-based collision warning system as standard

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The A-Class provides its drivers with comprehensive support and protection by means of numerous driving assistance systems, from drowsiness detection with ATTENTION ASSIST to proximity control with DISTRONIC PLUS. These assistance systems, which until now were reserved for higher vehicle segments, are based on state-of-the-art radar, camera and sensor technology and are designed to address the common causes of accidents, such as inadequate distance, fatigue and darkness.

In an innovative move in the compact segment, the A-Class is equipped as standard with a radar-based collision warning system with adaptive Brake Assist, a combination which lowers the risk of rear-end collisions. The COLLISION PREVENTION ASSIST system gives a visual and audible warning to alert a possibly distracted driver to identified obstacles, and prepares Brake Assist for the most precise braking response possible. This is initiated as soon as the driver operates the brake pedal decisively.

Unlike other assistance systems in compact-class vehicles already in the market, COLLISION PREVENTION ASSIST is not intended exclusively to minimise minor accident damage in an urban driving context. Instead, this innovative solution aims to provide protection against typical rear-end collisions in hazardous driving situations at speeds above 30 km/h. Field tests carried out by Mercedes-Benz in Europe, the US, Japan and South Africa over a total distance of more than 4.5 million kilometres since 2005 confirm that the most critical rear-end collision scenarios arise at speeds above 30 km/h.

Mercedes-Benz expects that COLLISION PREVENTION ASSIST will have a significantly positive effect on real-world accidents comparable to that seen following the introduction of ESP® as standard. Test results reinforce this view: tests involving 110 car drivers in the dynamic simulator saw the accident rate fall from 44 to 11 percent in three typical situations thanks to the combination of collision warning and adaptive braking assistance.

The radar-based COLLISION PREVENTION ASSIST system with adaptive Brake Assist:

- can recognise an inadequate distance from a vehicle ahead in the speed range between 30 and 250 km/h and warn the driver;

- can recognise when the gap is decreasing. In case of a detected imminent danger of collision, the driver is provided with a visual and audible warning;

- can recognise stationary objects ahead of the vehicle at a speed of up to 70 km/h and issue corresponding warnings;

- can adapt the activation threshold for the warning and adaptive Brake Assist to given driving situations, e.g. bumper-to-bumper traffic;

- calculates the precise braking force ideally needed to avoid an accident when danger of collision is detected and makes best possible use of any distance remaining. This means that the driver behind also has a better chance of avoiding a rear-end collision.

The brake pressure is adjusted if the situation changes – if the vehicle ahead accelerates, it is decreased to the level the driver requires; if the distance to moving and stopping vehicles decreases, the brake pressure is increased further. When the vehicle is equipped with PRE-SAFE®, COLLISION PREVENTION ASSIST provides one of the activation parameters for the anticipatory safety systems, such as the belt tensioners.

Electronic helpers: all the other assistance systems at a glance

Active Parking Assist, which is available as an option for the A-Class, has been developed on the basis of the PARKTRONIC system familiar from other model series. Ten ultrasonic sensors mounted in the front and rear bumpers measure the length of potential parking spaces at the left and right sides of the road. Once a suitable space has been identified, the driver stops the vehicle, selects reverse gear and activates the automatic parking assistance system via the controls on the multifunction steering wheel. The system calculates a suitable manoeuvring pattern with a maximum of five moves to complete the parking operation. The driver is assisted by the automatic actuation of the electromechanical steering during the parking process but still has to operate the accelerator and brake. The speed is limited to 10 km/h during the parking process. Parking in spaces situated along slightly curved roads is also supported.

Automatic steering to exit the parking space is a new subfunction. If the vehicle has been parked using Active Parking Assist, the vehicle can be steered out of the parking space in the direction corresponding to the activated direction indicator. Here, too, the driver has to operate the accelerator and brake. As soon as the vehicle has assumed a sufficient angle to exit the parking space in one straight move, the wheels are set to the straight ahead position, the process ends and the driver assumes steering control again. The process is completed at the latest when the vehicle is at an angle of 45 degrees relative to the starting position.

The democratisation of safety comprises a series of additional assistance systems:

- Adaptive Highbeam Assist: when vehicles are detected ahead of or oncoming to the vehicle, this system automatically dips the beams and adjusts the range of the headlamps appropriate to the distance. The driver benefits from a longer dipped beam range and does not generally need to switch manually between main and dipped beam.

- Blind Spot Assist: employs two additional radar sensors at the rear of the vehicle to warn the driver before a lane-change if a vehicle has been detected in the exterior mirror's blind spot.

- Lane Keeping Assist: a camera behind the windscreen recognises clear carriageway markings and can give a warning if the car is about to leave its lane unintentionally.

- ATTENTION ASSIST(standard): provides a warning when typical signs of drowsiness are detected. The system's highly sensitive sensors observe the driver's behaviour and can recognise – especially on the basis of how the steering wheel is being moved – if the driver is becoming drowsy or inattentive.

- Speed Limit Assist: a camera fitted behind the windscreen detects speed limit signs at the roadside and compares this data to information contained in the GPS system or the digital map. The relevant speed limit is then displayed in the instrument cluster.

- Brake hold function: when stopping, for example at traffic lights, the driver merely has to press the brake pedal slightly more firmly. They can then take their foot off the brake pedal and the brake will remain engaged until they move off again. The brake is released automatically when the driver steps on the accelerator.

- Hill-Start Assist: this function is able to prevent the vehicle from rolling back unintentionally when moving off on an uphill slope.

- Reversing camera: integrated in the handle strip on the tailgate, the reversing camera features a wide-angle lens. When reverse gear is engaged, the image from the camera is transmitted to the screen of the Audio 20 system or the COMAND system. Static and dynamic guide lines assist the driver during manoeuvring.

- DISTRONIC PLUS: the radar-based adaptive cruise control supports the driver at speeds between zero and 200 km/h by maintaining the distance to the vehicles in front. In doing so it is able to apply the brakes to bring the vehicle to a complete standstill and also accelerate it again. As a result, the system is also particularly convenient in stop-and-go traffic. If the system detects that the distance is being reduced too quickly, it warns the driver with both visual and audible signals.

- Cruise control with SPEEDTRONIC: the cruise control maintains the pre-set speed. The additional SPEEDTRONIC function ensures that the stored speed is not exceeded. Both functions come as standard with the 7G-DCT dual clutch transmission and are optionally available for the models with manual transmission.

* Official photos and details courtesy of Mercedes-AMG GmbH *

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