1. A vehicle comprising: an imaging means; an image capturing means which captures a color image of a road via the imaging means; a feature value calculation means which calculates a feature value of each pixel corresponding to the color of a road sign on the road from the color components of each pixel in the color image so as to reduce the effect of brightness on the color components; and a road sign detection means which detects the road sign on the road from the feature image in which the feature value of each pixel in the color image is arranged so as to match with the position of each pixel in the color image.