Principle for LDW
(The figure is schematic - not model specific.)
LDW consists of a camera that detects the side lines painted on the road/lane.
If the vehicle crosses the left or right-hand side line of the carriageway without due cause then the driver is alerted by an acoustic signal.
The driver is only warned once each time the wheels cross a line. So there is no acoustic alarm when there is a line between the car's wheels.
LDW is merely a driver's aid and does not engage in all driving situations or traffic, weather or road conditions.
The driver always bears ultimate responsibility for ensuring that the vehicle is driven safely and that applicable laws and road traffic regulations are followed.