2019 Audi A5 Sportback — Owner's Manual
Active lane assist (lane departure warning) detects lane marker lines within the limits of the system using a camera in the windshield. If you are approaching a detected lane marker line and it appears likely that you will leave the lane, the system will warn you with corrective steering. You can override this steering at any time. If you pass over a line, the steering wheel will vibrate lightly.
In order for this warning vibration to occur, it must first be switched on in the Infotainment system. Active lane assist is ready for operation when the lane marker line is detected on at least one side of the vehicle. The system is designed for driving on express ways and highways and therefore only activates at speeds above approximately 40 mph (65 km/h).