Traffic signal using mixed controller operations

An actuated controller performs well when the traffic is light to medium. When the traffic volume increases and one or more phases of an actuated controller reach the maximum green interval, the controller performance starts deteriorating. The green intervals no longer remain proportional to the traffic demand. A knowledge-based expert system (KBES) has been developed that implements the logic of switching controller operation from actuated to pretimed during heavy traffic conditions and vice versa. The KBES is called signal control at isolated intersections, version II (SCII-2). It is developed for adaptive signal control operation. The aforementioned switching capability is a part of its realtime control strategies. Different field tests are made to validate and calibrate the switching logic of this KBES. The field test indicates that during heavy traffic flow, a pretimed controller performs better than an actuated controller. Thus, the appropriateness of switching signal operation from one mode to the other is verified.