A front radar recognizes a still object. A process generates a still object map that shows a relative position between the still object and a subject vehicle. The process groups still objects in the still object map. In terms of each individual still object group, the process selects a left or right evaluation map depending on whether the still object group is positioned to the left or right side of a road. The process defines an additive value for the still object group based on the distance between the vehicle and the still object group and based on the vehicle speed. The process adds the still object group's additive value to the selected evaluation map. The process subtracts a subtractive value from part of the evaluation map where no values are added. The process recognizes a road shape based on the evaluation map.