In this article, a method is presented for detecting vehicles in image sequences without prior knowledge about the position of the road. A single camera placed in a moving vehicle provides image data. For the detection of midrange and distant vehicles, a combination of three clues is used: shadow, entropy, and horizontal symmetry. To detect passing vehicles, a temporal differencing and projected motion is used. The algorithms are tested by means of many different experiments. These experiments illustrate the robust and accurate performance of both approaches.