A CCD camera or equivalent sensor is mounted on a vehicle and used to detect lane markings (usually the white or yellow painted lines) on a roadway. An electric motor coupled to a steering system is used to provide a torque input to the steering, which may either assist or oppose the steering torque from a driver. A steering controller is designed to assist the driver to maintain the vehicle lane position by holding the vehicle at a target point using a biasing torque. The controller resumes application of the biasing torque upon expiration of a predetermined period of delay time since a change from the absence of detection of lane marking to the presence of detection of lane marking after the presence of detection of lane marking that continues for a period of time less than a predetermined period of time has occurred a predetermined number of times within a predetermined period of monitoring time or the absence of detection of lane marking continues for a predetermined period of time.