Automated estimation of average stopped delay at signalized intersections using digitized still-image analysis of actual traffic flow

Average stopped delay for a given signalized intersection approach is the average time a vehicle waits at a traffic light and constitutes a part of the measure of effectiveness of signalized intersections. The exploratory work done by two of the writers of this paper using images created by the animation feature of CORSIM traffic simulation software indicated that such application can actually produce stopped delay estimates commensurate with the results of the Institute of Transportation Engineers (ITE) method. However, CORSIM simulation images do not have parallax problems, and vehicle color and size and pavement color were practically the same for the entire evaluation field. The three methods (gap, gap-hybrid, and motion) developed in this study are able to overcome these problems associated with actual traffic flow images at an acceptable level. The methods were tested with two image data sets taken at two different locations with different camera angles. The performance of the three methods varies depending on the quality of image, camera angle, and calibrated parameter values used for each method, but in both cases they were able to produce average stopped delays similar to those estimated by the ITE manual method. At present the software that executes the three methods allows the user to analyze one approach lane at a time using digitized still images taken from analog video films; however, the software can be expanded to analyze multiple approach lanes and digital images dynamically fed by digital traffic monitoring cameras. With this automated procedure the traffic engineer can estimate average stopped delays in his or her office, greatly saving time, money, and the manpower necessary for conducting field data collections.