Vehicle Speed Measurement Based on Camera Calibration

Road traffic injuries cause considerable economic losses to individuals, their families, and to nations as a whole. Every year the lives of more than 1.25 million people are cut short as a result of a road traffic crash. A common cause of accidents is driving faster than one can stop within their field of vision. Measuring a vehicle's speed using video data is an important technique in determining the cause of a traffic accident. When on-site distance measurement cannot be carried out for a video recorded by a surveillance camera, the speed of a vehicle moving along a straight line in the video can be measured by selecting 2 reference points on the body of the vehicle and computing the speed of the vehicle during the time when the part of the vehicle between the reference points passed an environment point. The 2-reference-point method is widely used in traffic accident investigations in China. However, in real-world applications it often lacks high accuracy. In this paper we propose an improved method based on camera calibration. The proposed method selects 4 coplanar points on the body of the vehicle and computes their world coordinates by camera calibration. The speed is measured based on the movements of the 4 points. Experiments confirmed that the proposed method outperforms the 2-reference-point method.