Collision Warning System, Basic Function - GF54.70-P-9900A

Model All (4xWD) 

Model All (CAR) 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 
  • Distance warning 
  • Collision warning 
  • Autonomous emergency braking 
  • Situation-based brake force boosting 
  • End of traffic jam emergency braking function 
  • Cornering emergency braking function 
  • Intersection function 
  • System limits 

General 

The collision warning system monitors the traffic area using the radar sensor behind the radiator grille, using the multi-MODE radar sensors depending on the model series involved or, depending on the equipment installed, using the multifunction camera behind the windshield. Using the movement profile, the multifunction camera is able to distinguish between pedestrians, cyclists and vehicles.

In the event of an imminent collision, the system warns the driver and, in an emergency, brakes autonomously. If the driver himself brakes, the system supports the brake request depending on the respective situation.

The sensitivity of the collision warning system can be adjusted in three stages.

Thanks to the extensive road space monitoring, not only collisions with vehicles ahead but also with vehicles crossing in front (depending on the equipment installed) can be avoided.

The DISTRONIC PLUS and Active Brake Assist systems (vehicles without Driving Assistance Package) can use the multifunction camera to record the area in front of the vehicle (e.g. brightness, objects or traffic signs).

Vehicles with a Driving Assistance Package can also use the multifunction camera to detect the distance to an object, as well as its height above the roadway, and determine its direction of movement on the horizontal, vertical and longitudinal axis (longitudinal axis of an object). This then clearly recognizes whether an object is moving and if so, where to. For example, the exact impact location for a collision can be calculated which in turn enables the time remaining until the point of impact to be used to maximum effect for safety precautions.

The end-of-tailback emergency braking function on vehicles with Driving Assistance Package brakes the vehicle if there is no possibility of avoiding a collision, and can in this way prevent accidents or minimize their severity. To this end, the classic brake cascade starts earlier. This means that more speed can be dissipated.

Function requirements 

• Engine running or drive train operational.
• Collision warning system activated.
• Vehicle not moving backward (defined by wheel rotation direction).
• Soiling and function test of radar sensor completed.
• Soiling and function test of multifunction camera completed (depending on equipment installed).
• No tight bends.
• The driver must be wearing their seat belt for autonomous emergency braking.

Function 

The radar sensor and the multifunction camera (depending on the equipment installed) monitor the road space ahead of the vehicle.

Depending on the vehicle equipment, the controller unit in the radar sensor (vehicles without Driving Assistance Package) or the intelligent driving control unit (vehicles with Driving Assistance Package) evaluate the data from the two sensors. If a hazardous situation is detected, the system warns the driver of an imminent collision. If the situation worsens further, the system initiates autonomous braking.

The collision warning system is switched on each time the ignition is started. The driver can operate the system via the multimedia system.

The following settings are possible:

• "Early" setting: The intervention points have a very sensitive setting. This setting enables the highest possible safety by the system. In some situations, however, this may be considered obtrusive.
• "Medium" setting: The intervention points have the best possible configuration for maximum safety without obtrusive interventions. This setting is set automatically when the system has been switched off before an ignition change.
• "Late" setting: The intervention points are configured to occur significantly later. It is recommended that this setting only be used when utilizing a very sporty driving style.
• "OFF" setting: When switched off, the distance warning function and autonomous emergency braking is deactivated.

Distance warning 

The distance warning is issued as soon as the time interval to the vehicle driving in front falls below a certain value, i.e. the safe distance becomes too small. The warning is displayed visually in the form of a warning lamp. The static distance warning works for moving vehicles in a vehicle speed range of 30 to 250 km/h.

Collision warning 

The collision warning is triggered as soon as the vehicle begins approaching the detected vehicle driving in front too quickly or with excessive acceleration. In this case, both a visual warning and a warning tone are output. A dynamic distance warning can be output as of a vehicle speed of approx. 7 km/h.

The types of road users and the maximum speeds that the system supports can be found in the vehicle's specific operator's manual.

Autonomous emergency braking 

An autonomous brake application is initiated if the driver does not respond to collision warnings. The vehicle is braked heavily. The consequences of a potential rear-end collision or of an accident involving pedestrians or cyclists who cross the road without due attention or who are overlooked by the driver are mitigated. The driver is also warned of the initiated braking operation by haptic means. Autonomous brake application can take place as of a vehicle speed of approx. 7 km/h.

Partial braking occurs first if the driver does not respond in the event of a collision warning.

Maximum full-stop braking occurs if partial braking is not sufficient to avoid a collision or if the driver does not react.

A brake application enacted by the Active Brake Assist can be aborted by releasing the brake pedal or accelerating significantly (e.g. kickdown).

The types of road users and the maximum speeds that the system supports can be found in the vehicle's specific operator's manual.

An autonomous braking application may be enough at low speeds to avoid a rear-end collision or a collision.

If the driver depresses the brake pedal during autonomous brake application, situation-based brake force boosting takes over and can decelerate the vehicle up to maximum full-stop braking.

If autonomous braking application or situation-based brake force boosting exceeds certain deceleration values, additional functions such as seat belt tensioning are activated.

Situation-based brake force boosting 

Situation-based brake force boosting is triggered after dynamic collision warning if the driver brakes sharply. Brake force boosting amplifies the brake pressure generated by the driver via the brake pedal.

To keep the impact speed as low as possible, the collision warning system with the maximum possible deceleration up to the point of collision.

Intervention by the situation-based brake force boosting can be overridden by the driver at any time. The driver's request is given priority if the driver wants to brake more strongly than the system. The driver can cancel intervention at any time by releasing the brake, depressing the accelerator pedal or steering and thereby attempting to avoid the obstacle.

If the braking procedure exceeds certain acceleration values, PRE-SAFE ® functions are also activated. Situation-based brake force boosting can take place as of a vehicle speed of approx. 7 km/h.

The types of road users and the maximum speeds that the system supports can be found in the vehicle's specific operator's manual.

If braking assistance or automated brake application has been canceled or completed, a display appears that indicates the system reaction.

End of traffic jam emergency braking function 

Vehicles with Driving Assistance Package.

The end-of-tailback emergency braking function detects end-of-tailback scenarios where there is either restricted or no evasive maneuvering possibilities. Here, the road space monitoring function defines the source of the risk of collision:

• Vehicle in own lane
• Vehicles in adjacent lanes
• Guardrails

In detected end-of-tailback scenarios where evasive steering is not an option, the collision warning system initiates early emergency braking, which can reduce the vehicle speed by up to 100 km/h. The end of traffic jam emergency braking function is active in a vehicle speed range of roughly 7 to 130 km/h.

Example illustration of cornering emergency braking function 

Courtesy of MERCEDES-BENZ USA

Cornering emergency braking function 

Vehicles with Driving Assistance Package, as of model 167 market launch

The cornering emergency braking function detects risks of collisions with oncoming vehicles (vehicle-specific also bikes and pedestrians) when turning into the oncoming lane.

Up to the market launch of model 223 (up to Driving Assistance Package Gen5) an autonomous brake application is only initiated if the vehicle was braked to a standstill before crossing over the lane marking.

The cornering emergency braking function is active in a vehicle speed range of roughly 2 to 12 km/h.

Example illustration of intersection function 

Courtesy of MERCEDES-BENZ USA

Intersection function 

The cross-traffic function detects crossing road users and brakes automatically when a potential collision is detected.

Braking for road users crossing over a roadway takes place up to a vehicle speed of 120 km/h.

Fast-moving and crossing road users are detected by the front corner radar sensors.

System limits 

The system may be impaired or inoperative in the following situations, for example:

• In the case of snow, rain, fog, heavy slush, dazzle, direct sunlight or varying light conditions.
• If the sensors are dirty, fogged up, damaged or obscured.
• If the sensors are disrupted by other radar sources, e.g. in the event of strong radar feedback in multi-level car parks.
• If tire pressure loss or a defective tire has been detected and displayed.

The system may not react correctly in certain circumstances:

• In complex traffic situations in which objects are not always clearly identifiable.
• In tight-radius bends.

	Function schematics
	Collision warning system, function schematic	Model 118, 167, 177, 243, 247, 293 with code 258 (Active Brake Assist System) Model 213, 238, 257, 290 as of model year 2021 with code 258 (Active Brake Assist System)	PE54.70-P-2500-97A
		Model 118, 167, 177, 243, 247, 293 except code 258 (Active Brake Assist System) Model 213, 238, 257, 290 as of model year 2021 except code 258 (Active Brake Assist System)	PE54.70-P-2500-97B
		Model 223, 297	PE54.70-P-2500-97C
		Model 192, 206, 214, 232, 236, 254, 294, 295, 296	PE54.70-P-2500-97D
	Additional basic functions
	Intelligent driving control unit, basic function		GF30.30-P-9890A
	Distance control controller unit, basic function		GF30.30-P-9891A
	Collision warning system controller unit, basic function		GF30.30-P-9893A
	Brakes, basic function		GF42.00-P-9900A
	Traffic area monitoring, basic function		GF54.71-P-1000A
	Intelligent driving radar sensor, basic function		GF54.71-P-2005A
	Front multifunction camera, basic function		GF54.71-P-9890A