LANE BOUNDARY DETECTOR

A boundary detector includes a candidate line detecting unit that detects a candidate line of a lane boundary position drawn on the road surface based on image information from a camera. The detector also includes a lane boundary position selecting unit that selects the lane boundary position based on the candidate line; an additional lane boundary position selecting unit that selects a lane boundary position of an additional lane that is added to a main lane based on the candidate line; and an additional processing unit that stops adopting the lane boundary position for a predetermined time period when the additional lane boundary position selecting unit selects a lane boundary position of the additional lane.