Redesign Frequency for Fixed-time and Vehicle-actuated Signal Controllers at A Right-turning Channelized Intersection

Abstract

Fixed-time control and vehicle-actuated control are two main signaling strategies implemented at intersections for urban traffic management. The timing and structure of the controllers are usually designed optimally based on average historical demand patterns at the intersection. Under the premise of performance quality assurance, both fixed-time and vehicle-actuated controllers can accommodate a certain degree of demand fluctuations. As a matter of fact, the demand change can be considerable over the years, which could exceed their capacities in adapting such degree of demand change, and thus the signal controllers should be regularly updated to fit the latest demand. To some extent, how much demand change can be adapted by both types of the signal controllers determines how frequent should the controllers be checked and improved. However, only qualitative comparison of the capabilities in demand adaptation between fixed-time and vehicle-actuated controllers are made in most of existing literatures, according to which vehicle-actuated controllers are expected to have higher capabilities in accommodating demand changes. In this research, a quantitative analysis and comparison were made for the fixed-time and vehicle-actuated controllers at a right-turning channelized intersection under various demand conditions. Since no useful studies could be found to predict the demand changes towards a specific intersection at current phase, the extra demand that could be accommodated by vehicle-actuated controllers were investigated instead. And it is found that the vehicle-actuated controllers can serve a 19% to 204% of more demand compared with the fixed-time controllers in scenarios defined in this research, according to which the redesign frequency can be further determined for both types of controllers to maintain comparable operation performance.