Mercedes-Benz

Function of Active Brake Assist

Active Brake Assist consists of the following functions:

Distance warning function
Autonomous braking function
Situation-dependent brake force boosting

Active Brake Assist can help you to minimise the risk of a collision with vehicles, cyclists or pedestrians, or reduce the effects of such a collision.

If Active Brake Assist has detected a risk of collision, a warning tone sounds and the warning lamp lights up in the instrument cluster.

If you do not react to the warning, autonomous braking can be initiated in critical situations. In especially critical situations, Active Brake Assist can initiate autonomous braking directly. In this case, the warning lamp and warning tone occur simultaneously with the braking application.

If you apply the brake yourself in a situation detected as critical by Active Brake Assist, or apply the brake during autonomous braking, situation-dependent brake force boosting occurs. The brake pressure increases up to maximum full-stop braking if necessary.

If autonomous braking or a situation-dependent braking boosting effect has occurred, the warning lamp flashes and goes out after a short time.

Vehicles with PRE-SAFE®: if the autonomous braking function or the situation-dependent brake force boosting is triggered, additional preventive measures for occupant protection (PRE-SAFE) may also be initiated More.

WARNING Risk of an accident caused by limited detection performance of Active Brake Assist

Active Brake Assist cannot always clearly identify objects and complex traffic situations.

Always pay careful attention to the traffic situation; do not rely on Active Brake Assist alone. Active Brake Assist is only an aid. The driver is responsible for maintaining a sufficiently safe distance to the vehicle in front, vehicle speed and for braking in good time.

Be prepared to brake or swerve if necessary.

If the system is not available, an appropriate message appears in the multifunction display.

Observe the system limitations of Active Brake Assist. Due to the nature of the system, complex but non-critical driving conditions may also cause Active Brake Assist to intervene during braking.

The individual subfunctions are available in the following speed ranges:

Distance warning function

The distance warning function warns you in the following situations:

From a speed of approximately 30 km/h, if over several seconds the distance maintained to the vehicle travelling in front is insufficient for the driven speed. The warning lamp in the instrument cluster then lights up.
From a speed of approximately 7 km/h, if your vehicle is critically close to a vehicle or pedestrian. An intermittent warning tone sounds and the warning lamp in the instrument cluster then lights up.

Brake immediately or take evasive action, provided it is safe to do so and the traffic situation allows this.

The distance warning function can aid you in the following situations with an intermittent warning tone and a warning lamp:

Vehicles travelling in front: up to approximately 250 km/h
Stationary vehicles: up to approximately 80 km/h
Crossing vehicles: no reaction
Moving pedestrians/cyclists ahead: up to approximately 80 km/h
Crossing cyclists: up to approx. 60 km/h
Stationary pedestrians: no reaction

Autonomous braking function

The autonomous braking function may intervene at speeds starting from approximately 7 km/h in the following situations:

Vehicles travelling in front: up to approximately 200 km/h
Stationary vehicles: up to approximately 50 km/h
Crossing vehicles: no reaction
Cyclists ahead: up to approximately 80 km/h
Moving pedestrians/crossing cyclists: up to approximately 60 km/h
Stationary pedestrians: no reaction

Situation-dependent brake force boosting

Situation-dependent brake force boosting may intervene at speeds starting from approximately 7 km/h in the following situations:

Vehicles travelling in front: up to approximately 250 km/h
Stationary vehicles: up to approximately 80 km/h
Crossing vehicles: no reaction
Cyclists ahead: up to approximately 80 km/h
Moving pedestrians/crossing cyclists: up to approximately 60 km/h
Stationary pedestrians: no reaction

Cancelling a brake application of Active Brake Assist

You can cancel a brake application of Active Brake Assist at any time by:

Fully depressing the accelerator pedal or with kickdown.
Releasing the brake pedal.

Active Brake Assist may cancel the brake application when one of the following conditions is fulfilled:

You manoeuvre to avoid the obstacle.
There is no longer a risk of collision.
An obstacle is no longer detected in front of your vehicle.

System limits

Full system performance is not available for a few seconds after switching on the ignition or after driving off.

The system may be impaired or may not function in the following situations:

In snow, rain, fog or heavy spray.
If the sensors are dirty, misted up, damaged or covered.
If the sensors are impaired due to interference from other radar sources, e.g. strong radar reflections in multi-storey car parks.
If a loss of tyre pressure or a defective tyre has been detected and displayed.
In complex traffic situations where objects cannot always be clearly identified.
If pedestrians or vehicles move quickly into the sensor detection range.
If pedestrians are hidden by other objects.
If the typical outline of a pedestrian cannot be distinguished from the background.
If a pedestrian is not detected as such, e.g. due to special clothing or other objects.
In bends with a narrow radius.

Following damage to the front end of the vehicle, have the configuration and operation of the radar sensor checked at a qualified specialist workshop. This also applies to collisions at slow speeds where there is no visible damage to the front end of the vehicle.