A camera reads the painted side lines of the road/lane. If the car is about to cross a side line then Lane Keeping Aid will actively steer the car back into the lane with a slight steering torque in the steering wheel.
If the car reaches or crosses a side line then Lane Keeping Aid will also alert the driver with vibration in the steering wheel.
LKA 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.