Development of an actuated traffic control process utilizing real-time estimated volume feedbback

Abstract

Actuated traffic controllers are intended to determine traffic conditions, in real-time by means of vehicle detection, and respond accordingly in order to maintain the highest reasonable level of efficiency under varying conditions. However, modern traffic controllers are essentially sophisticated electronic timers. Rather than merely responding to detector ablations, it is desirable to improve this system such that the controller has a goal to be achieved and acquires information about the present state of the system in the same units. The goal of this research was to develop an actuated traffic control process that could use estimated volumes in order to optimally operate the traffic signal in real- time in response to actual traffic demands, or a reasonable estimate of demand. Once the present and desired states of the system are known, the control changes necessary to move from the present state to the optimal target state can be determined. A further goal of this research was to establish the relationship between the traditional control parameter, passage gap and key operating parameters, in order to allow changes in signal operations to be made by means of passage gap adjustments. The relationships between passage gap and cycle length, green splits, and interval length were studied, and the cycle length relationship was formalized mathematically. The quantified form can then be used as a tool to adjust the signal performance to approach the desired operating state. Research was conducted with computer simulation, using both stand-alone software and a hardware-in-the-loop setup. Testing and comparison between methods validated the use of these models. Results indicated that the volume estimation methodology could be readily calibrated to provide good estimates of traffic volumes by movement. Furthermore, simulation results quantified the relationship between passage gap and cycle length, thereby establishing a mechanism by which to directly implement signal operating changes at an actuated traffic signal. The scope of the research dealt with only one traffic control sensor design configuration - that of 6th-foot stapling detection. The overall study results suggest that this design is operationally very efficient for minimizing delay, but provides little "dilemma zone'' protection for arriving motorists at low-volumes and high-speeds. The research results suggest that the operational results may have been different had other high-speed detection options been considered. This thesis also includes descriptions of lessons learned through the simulation process and recommendations for issues to be addressed in future research.