Measurement of Traffic Volume by Time Series Images Created from Horizontal Edge Segments

This paper presents the method to measure the number and speed of passing vehicles from the traffic surveillance camera. In the bird's-eye view image obtained by the inverse perspective mapping, vehicles traveling at constant speed move at constant speed which depends on the height from the road surface. Using this feature, the proposed method detects individual vehicles and calculates the vehicle speed. In the image taken from the back of the vehicle, the vehicle appears from the roof and the rear view of the vehicle appears gradually from the top to the bottom. For this reason, the proposed method detects the position of the horizontal edge segment in the bird's-eye view image and creates the time series image in which it's arranged in order of frame numbers. The trajectory of the position of the horizontal edge segment draws a straight line in the time series image when the vehicle moves at a constant speed in the measurement area. Therefore, the slope of the straight line, that is, the speed of the horizontal edge segment is calculated to separate vehicles. When the trajectory of the horizontal edge segment with higher speed appears, it's determined that a new vehicle has entered the measurement area. At this point, the number of vehicles is incremented and the speed of the vehicle is calculated from the slop of the previous trajectory. The proposed method is robust to overlap between vehicles and the sudden change in brightness. The processing speed is also lower than the video rate.