Comparative assessment of arterial operations under conventional time-of-day and adaptive traffic signal control

This paper compares three principal arterial corridors in Alabama under both conventional and adaptive traffic signal control (ATSC). The corridors differ in their physical and operational characteristics. The comparison is conducted through microsimulation analysis of each corridor under their latest time-of-day (TOD) signal operations compared with the same field conditions (i.e., traffic volumes, geometry, access management) operating under Sydney Coordinated Adaptive Traffic System (SCATS) control. The three corridors greatly differ in the traffic saturation levels. Thus, the objective of this paper is to analyze and compare the performance of SCATS under varying saturation conditions. The comparison is based on various performance measures, including travel time, delay, average speed, and queue lengths under TOD and SCATS control. Based on the data and analysis results, a general conclusion is reached that in addition to the traditional ways to assess network performance, a range of other performance measures at various scales (i.e., network, corridor, sub-corridor, intersection) should be used to evaluate ATSC depending on overall policy goals. Under SCATS control, shorter side-streets queue lengths and shorter cycle-to-cycle queue lengths contribute to the network-wide performance gains. The improved network-wide performance is also attributed to the lower delays on side-streets and left-turn movements with SCATS. However, SCATS shows immediately measurable operational improvements only on unsaturated networks. SCATS shows less direct improvements in the network-wide performance measures for saturated conditions due to less ability to adapt and give more constrained vehicle movements.