The idiomatic expression "to keep the car in one's lane" means to stay focused on what you are doing and not be distracted by other things. Full definition
The car also features the lane - departure warning system and the lane - keeping assist system, which alarm the driver and help keep the car in the lane it is currently maintaining. (serramonteford.com)
The technology automatically keeps the car in its lane and a safe distance away from the car in front in dense traffic. (digitaltrends.com)