REAL-TIME COORDINATED-ACTUATED TRAFFIC CONTROL DURING CONGESTED CONDITIONS

This research report summarizes findings from a research project that deals with real-time coordinated-actuated control during oversaturated traffic conditions on signalized arterials. It is organized into four chapters. Chapter 1 identifies operational problems associated with congestion and provides a summary of existing technology. Chapter 2 summarizes the results of field studies that measure headways during oversaturated traffic conditions. These field studies were conducted in Houston and Austin, Texas. The purpose of these studies was to investigate whether headways increased, decreased, or remained constant on approaches with long queue lengths and long green times. These studies show that driver expectancy plays an important role in determining headways. These studies also show that average headway is independent of a vehicle's position in queue; however, variations in headways increase for vehicles further back in the queue. Chapter 3 summarizes findings from simulation studies conducted to compare five coordination strategies for a five-intersection arterial with one oversaturated direction. The results of this study show that coordination of actuated signals for progressing traffic flow in the congested direction produces lower delays, fewer stops, and shorter queues. Chapter 4 presents the architecture of a real-time traffic control system for coordinated-actuated control, and discusses various issues related to demand estimation. This chapter also describes how these ideas are being implemented in Richardson, Texas, and concludes with the description of a prototype real-time graphical interface for use by operators.