Mercedes-Benz S-Class - DISTRONIC PLUS system limits | C216, W221

Distronic and Distronic Plus driving assistance systems
They regulate the distance to the vehicle in front and adjust the speed to the driving situation.
Both systems have their limitations.
Technical design of the adaptive cruise control:
The cover plate protects the radar sensor underneath.
The radar sensor is equipped with an integrated control unit, ...
... which monitors the area in front of the vehicle up to 150 meters away.
The advanced variant of adaptive cruise control is Distronic Plus.
Distronic Plus has two additional radar sensors.
They are available for model series C216 and W221.
The additional sensors increase the effective area together with the long-range sensor of the Distronic system.
Distronic Plus reacts as of a distance of 20 centimeters.
Distronic Plus is thus not only suitable for flowing traffic, ...
.. but also for stop-and-go traffic and convoy driving.
The control unit for the additional sensors is installed in the trunk on the right.
Due to country-specific regulations, the 24 gigahertz sensors are not available in every market.
Adaptive cruise control makes driving easier and safer.
The most important examples of the limits of the Distronic and Distronic Plus systems:
Switch on the Distronic at the cruise control lever. Set the target distance via the adjustment wheel.
"System limit in corners": Distronic in corners
Distronic orientates itself via the radar and steering wheel position.
If the steering wheel has not yet been turned, ...
... vehicles in front may not always be detected.
The driver must always be ready to brake in corners even with Distronic operating.
"System limit with stationary obstacles": Traffic circle with sign
During the approach, the radar sensors may detect the sign as an obstacle.
In this case, the PRE-SAFE brake or distance warner may warn of a collision.
When the steering wheel is turned, the system recognizes that the vehicle is in a corner.
The driver can switch off the collision warning.
Under the menu item "Assistance" - "PRE-SAFE brake", ...
... the collision warning and autonomous partial braking can be deactivated.
The Distronic remains functional.
The same applies when vehicles are queuing at a red traffic light.
They are detected by the Distronic but the system does not brake automatically.
An overtaking warning is issued. The driver must brake actively.
"System limit with unexpected braking": Overtaking warning in the event of sudden braking by vehicle in front
Distronic reacts to unexpected braking with only 30-40 percent of the braking power.
The driver must brake independently.
"System limit in cross traffic":
The cross traffic is only briefly detected within the radar cone, ...
... when it is already in front of the vehicle.
Be careful at intersections!
If Distronic is switched on, it may think that the road ahead is free.
The driver must be ready to brake to prevent misinterpretations.
"System limit for vehicles with insufficient width":
Cyclists and motorcyclists may not be detected by Distronic due to their width.
Distronic can only react to vehicles ...
... which are within the sensor detection range.
"System limit for vehicles cutting in or driving at an offset":
Be careful on two-lane roads!
Distronic orientates itself to the vehicle in front.
If a vehicle cuts in from the adjacent lane, it will only be fully detected by the radar at a late stage.
The distance will then be too short.
The driver must brake independently.
The same applies to vehicles driving at an offset.
Distronic cannot detect vehicles driving at an offset, ...
... if they are not within the effective range of the sensors.
"System limit when countersteering":
Be careful on road surfaces which drop off! Distronic orientates itself to the steering wheel position.
The driver may have to countersteer.
The Distronic may not recognize the vehicle in front, ...
... but the adjacent vehicle instead.
If Distronic orientates itself to adjacent vehicles on even road surfaces:
Check whether the suspension is misaligned or the radar sensor system is incorrectly calibrated.
Here are some more notes on adaptive cruise control in addition to the system limits:
As per the operating instructions, note the following:
Distronic shuts off in heavy snow or ice.
Distronic shuts off in the vicinity of radio astronomy stations.
Distronic uses the same frequencies as those used for radio astronomy.
To prevent interference, the Distronic as of modification year 2007 ...
... is automatically deactivated on vehicles with integrated navigation unit.
Otherwise, Distronic can be switched off manually.
The radar sensor system can be accessed in the instrument cluster under "Settings".

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