See also:

Deactivating HDC
Press the button again and the LED goes out. HDC is automatically deactivated above approx. 37 mph/60 km/h. ...

The concept
The system is functional at speeds beginning at approx. 20 mph/30 km/h. It maintains the speed that was set using the control elements on the steering wheel. The system brakes on downhill gradie ...

Close the windows and glasssunroof
Driving with the glass sunroof and windows open results in increased air resistance and raises fuel consumption. ...