Signal Group-based Look-ahead Traffic Signal Control

Abstract

Traffic signal controllers have been around since the late sixties of the 19th century and since then they have played an increasing role in (urban) traffic management. Over the years many different algorithms have been developed and in Dutch practice actuated control is mostly used. Actuated control and other similar approaches apply variable green times to handle demand fluctuation, which leads to a reduction of the delay for vehicles in comparison to e.g. fixed-time control, however, in actuated control it is difficult to accurately predict control decisions. This study proposes a new traffic signal control algorithm that creates a planning of control decisions based on expected vehicle arrivals. By doing so, predictability of control decisions increases, while no sacrifices need to be made regarding the optimality of the control policy. Since certain errors such as inaccurate queue discharge rates are incorporated in the planning of control decisions, a second algorithm is required that adjusts the planning of control decisions to actual traffic conditions. Using an N65 case study intersection the performance of the new traffic signal control algorithm is compared to other algorithms. Depending on the availability of vehicle arrivals and the composition of traffic flows at the intersection, the new algorithm outperforms standard Dutch actuated traffic signal control in terms of overall delay by 3.1% to 4.7%. A range of improvement possibilities is suggested to ensure a greater reduction of the delay.