Active Steering Assist is country-dependent and only available for vehicles with the Driving Assistance Package.
Active Steering Assist is operational at speeds up to 210 km/h and helps you to stay in the centre of the lane by means of moderate steering interventions. It uses the vehicle in front and the lane markings as a reference depending on the driven speed.
When the system is actively steering, the 
symbol is shown in green in the multifunction display.
The driver is required to keep their hands on the steering wheel at all times and to be able to intervene at any time. The driver must expect a change from active to passive mode or vice versa at any time.
If the system reaches a system limitation or the driver has not steered the vehicle for a considerable period of time or has removed their hands from the steering wheel, the system will, depending on the situation, first alert the driver with a visual warning. Display 
appears in the multifunction display. If the driver still does not steer the vehicle, or has still not taken hold of the steering wheel, a repeated warning tone sounds in addition to the visual warning message to remind the driver to take control of the vehicle.
The driver steers the vehicle.
The driver presses a steering wheel button or operates Touch Control.
Active Steering Assist is only an aid. The driver is responsible for the distance to the vehicle in front, for vehicle speed, for braking in good time and for staying in lane. Before changing lanes, the driver must make sure that the neighbouring lane is free (glance over the shoulder).
Active Steering Assist has a limited steering torque for lateral guidance. In some cases, the steering intervention is not sufficient to keep the vehicle in the lane.
If the detection of lane markings and vehicles ahead is impaired, Active Steering Assist switches to passive mode. The system provides no support in this case. During the transition from the active to passive status, the symbol is shown as enlarged and flashes yellow. Once the system is passive, the symbol is shown as grey in the multifunction display.
If there is poor visibility, e.g. due to insufficient illumination of the road, or due to snow, rain, fog or heavy spray.
If there is glare, e.g. from oncoming traffic, direct sunlight or reflections (e.g. if the road surface is wet).
If the windscreen is dirty, misted up, damaged or covered, for instance by a sticker, in the vicinity of the camera.
If no, or several, unclear lane markings are present for one lane, e.g. in a construction area.
If the lane markings are worn away, dark or covered up, e.g. by dirt or snow.
If the distance to the vehicle in front is too small and the lane markings thus cannot be detected.
If the lane markings change quickly, e.g. lanes branch off, cross one another or merge.
If the roadway is narrow and windy.
If there are highly variable shade conditions on the roadway.
If there are obstacles such as object markers on the lane or projecting out into the lane.
If you are driving along very tight bends.
If you are towing a trailer.
If you actively change lane without switching on the turn signal indicator.
If the tyre pressure is too low.