See also:

The concept
The parking brake is primarily intended to prevent the vehicle from rolling while parked; it brakes the rear wheels. ...

Configuring the prewarning
After the warning function is switched on, the following can be set via the iDrive: The prewarning can be switched on/off. The time of the prewarning can be set. These settings have no effe ...

End of warning
The warning ends: Automatically after approx. 3 seconds. When returning to your own lane. When braking hard. When using the turn signal. ...