Degree of Saturation Estimation Using the Average Travel Time at a Signalized Intersection

The rapid development of traffic information technology has enabled the collection of segment and location-based data, in addition to spot data. Therefore, it is now possible to collect data that can represent the condition of a road section, such as travel time. Although the use of travel time is noted in previous studies, they do not consider interruptions to traffic flow, such as those at signalized intersections. This paper proposes algorithms to estimate the degree of saturation (DoS), defined as the ratio of demand flow to capacity, using the average travel time at signalized intersections. The average control delay is first calculated using the average travel time at signalized intersections in a roadway section. The DoS is then determined using an analytic delay model that describes the relationship between average control delay and DoS. At this time, if an initial queue occurs, the delay caused by the initial queue is adjusted. Furthermore, simulation and field test analyses confirm the accuracy of the algorithms, and that the average travel time can estimate DoS. The findings can be used for an improved adaptive signal control system operation and help establish a signal optimization policy for future research.