This guide presents a rational approach for identifying traffic control strategies for mitigating oversaturated conditions at signalized intersections. This guide will discuss the following components of the rational approach: • Diagnosis of the type and causes of the oversaturated condition. • Identification of appropriate operational objective(s) based on the observed condition(s). • Identification of appropriate strategies to address the situation. • Identifying any necessary infrastructure, equipment, or software requirements for each strategy. The intended audience for this guide is a practicing traffic engineer with responsibility for designing and implementing traffic signal system timing, phasing, sequencing, and scheduling. The guide focuses on common traffic control strategies and features available in the majority of traffic controllers. The guide does not address freeway operations, geometric reconfiguration, re-routing, traveler information, or other strategies that seek to influence travel demand, departure time choice, or route choice. Nor does the guide explicitly address strategies or oversaturated conditions for buses, pedestrians, bikes, or trains. This guide assumes working knowledge of traffic signal system concepts and North American signal control terminology. We will refer to common terms such as phase, movement, ring, barrier, offset, split, and so on, without definition or further explanation. A glossary of terms is available in Appendix A. Additional information on terminology and concepts can be found in the Traffic Signal Timing Manual. New concepts and terminology will be defined and explained. The mitigating traffic signal control strategies noted in this guide are able to be implemented using actuated-coordinated traffic signal controllers that run patterns of timing parameters that can be changed by time-of-day or via detection inputs. A preliminary approach for determining green time adjustments on oversaturated routes is included in Appendix B. Other mitigations and rules of thumb noted in this guide link common controller capabilities to certain types of traffic scenarios. For some of the strategies, we have provided example results and application guidelines. An experimental mathematical optimization approach is documented in the final report for the research project. (Author/publisher)
Samenvatting