Comparison of Flow- and Bandwidth-Based Methods of Traffic Signal Offset Optimization

AbstractMethods of optimizing offsets in coordinated traffic signal systems can be grouped into two categories: bandwidth based and flow based (e.g., minimizing delay). To our knowledge, no studies have directly compared methods from both categories. This study fills this gap with quantitative comparison between flow- and bandwidth-based methods. This paper evaluates the performance of 11 methods of offset optimization, including several different objectives that make use of arrival profiles (e.g., maximizing arrivals on green, minimizing delay, minimizing the number of stops) and several different methods of bandwidth maximization. These are compared against a default scenario with all offsets set to zero, and a manual method for determining offsets. An eight-intersection simulation network is used for comparison. The outcomes are compared in terms of the effective bandwidth, delay and stops, arrivals on green, and travel time. The results show that flow-based methods that incorporate models of delay and/or stops tend to yield more directionally balanced travel delays as well as lower total arterial delay and stops. Bandwidth-based methods achieved higher bandwidth and arrivals on green. Some additional comparisons are made among the 11 tested methods.