The radar-based brake assist system.

Mercedes-Benz Intelligent Drive


The Brake Assist system BAS PLUS – part of the optional DISTRONIC PLUS system – can help to prevent a rear-end collision or at least reduce the impact speed should the collision prove unavoidable.

Sensors that monitor the area around the vehicle and recognize potential dangers at lightning speed are at the core of the BAS PLUS assist system, which is available with the optional DISTRONIC PLUS. Two radar systems are available for Brake Assist PLUS.

One long-range sensor is located beneath the radiator grille. It scans the area in the front of the car at a scanning angle of 18 degrees up to a range of 200 m (for models from 2009 on; previously 150 m) and across up to three traffic lanes.



BAS PLUS employs the same watchful "eyes" as DISTRONIC PLUS: two radar systems which carry out long-, mid- and close-range monitoring of the area in front of the vehicle. These systems are particularly good at detecting moving objects ahead, calculating their distance in front and determining the relative speed between vehicles in front and one's own car.
When the assistance system recognises an impending rear-end collision on the basis of this information, Brake Assist PLUS goes into action. The electronics then calculate the necessary deceleration automatically. When the driver subsequently steps firmly on the brake pedal, BAS PLUS recognises the driver's braking intention and optimises the brake pressure automatically. BAS PLUS enables controlled precision braking according to the given speed and distance and increases the brake power as necessary – applying full emergency braking in the most extreme cases.
BAS PLUS intervenes only when the driver's braking response is not sufficient. When the driver takes his foot off the brake or the radar shows that the way ahead is now clear, BAS PLUS ends its assistance function.

Detailed information


Changes may have been made since these images and films were produced.

BAS PLUS uses the same attentive "eyes" as the DISTRONIC PLUS system, i.e. two radar systems that monitor short, medium and long-range distances ahead of the vehicle. One thing the systems do extremely well is detect objects in front of the vehicle and calculate their distance and relative speed compared with the system’s vehicle.


Should the distance between the vehicle and the detected object decrease to an extent that equates to a potential collision, Brake Assist PLUS will go into action by issuing a visual warning on the instrument cluster display and sounding an alarm via the car speakers. At the same time, the electronics system calculates the braking deceleration required to avert the accident. If the driver hits the brakes hard, BAS PLUS recognizes this and automatically optimizes the braking pressure needed to prevent an impact.


Depending on the car’s speed and its distance from the vehicle in front, BAS PLUS can either implement systematic breaking or, if necessary, increase braking power up to maximum force. BAS PLUS engages only if the driver’s braking reaction is not sufficient to prevent an accident. BAS PLUS shuts off braking support if the driver stops braking or the radar no longer detects an object in front of the car.



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