A Cheap System for Vehicle Speed Detection

The reliable detection of speed of moving vehicles is considered key to traffic law enforcement in most countries, and is seen by many as an important tool to reduce the number of traffic accidents and fatalities. Many automatic systems and different methods are employed in different countries, but as a rule they tend to be expensive and/or labor intensive, often employing outdated technology due to the long development time. Here we describe a speed detection system that relies on simple everyday equipment - a laptop and a consumer web camera. Our method is based on tracking the license plates of cars, which gives the relative movement of the cars in the image. This image displacement is translated to actual motion by using the method of projection to a reference plane, where the reference plane is the road itself. However, since license plates do not touch the road, we must compensate for the entailed distortion in speed measurement. We show how to compute the compensation factor using knowledge of the license plate standard dimensions. Consequently our system computes the true speed of moving vehicles fast and accurately. We show promising results on videos obtained in a number of scenes and with different car models.