Autonomous navigation is important to robotize agricultural vehicles. This paper discusses a development of an image processing method to discriminate between traversable region (furrow) and non-traversable region (ridge) in ridged fields with no crops. Our method consists of 3 parts. First, images were separated into images with shade and images with no shade by gray level histograms. Next, as for images with shade, colour information was used to discriminate between traversable region and non-traversable region. On the other hand, as for images with no shade, texture was focused on. In this research, variance was used as a texture description. The proposed method was tested on images acquired by a camera, taken of different fields and under different light conditions. Our method discriminated between traversable region and non-traversable region successfully. Copyright © 2013 IFAC.