Principle for LDW
(The figure is schematic - not model specific.)
A camera reads the side lines of the road/lane.
If the car crosses one of the side lines the driver is alerted with 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.
Lane assistance is merely a driver 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.