In ITS, vehicle detection is very important research field, which can provide the relevant information, such as position, shape, size, and so on. How to segment the vehicle is the key in vehicle detection. A simple vehicle segmentation algorithm based on computer vision is proposed in this paper. Firstly, an effective preprocessing method to eliminate the affection of different scale gray pixels in different region, which can make the image be easily binarized; Secondly, a small threshold can be set to binarize the preprocessed image; After that, in order to avoid the small regions enclosed in big region, a inner region filling algorithm is presented; Thirdly, the image processed by first and second step can be easily segmented; Lastly, several transportation scene images are used to test the proposed algorithm, the result indicate the validity of the proposed segmentation algorithm.