UNDERSTANDING CONTROLLER SETTINGS

To safely and efficiently control vehicle traffic, traffic engineers must understand the functions of various controller settings for traffic signals. Two basic types of intervals control vehicle traffic and are timed by a traffic signal controller: safety-related intervals and discretionary intervals. Safety-related intervals provide for safe vehicle operation at intersections and discretionary intervals establish efficient traffic movement by carrying out the operating policy for that intersection. This article describes the appropriate use of these intervals as well as the use of gap-reduction settings.