The defined point that creates an association between the local clock at a given signalized intersection and the master clock. Offset Reference Point (Coordination Point) The time relationship between coordinated phases defined reference point and a defined master reference (master clock or sync pulse). referenced during coordinated operations. The background timing mechanism within the controller logic to which each controller is. Essentially, the split time is treated as a maximum amount for the non-coordinated phases.
Under this mode, non-coordinated phase times are limited to their defined split amount of time and all unused time is dedicated to the coordinated phase. Floating Force-offĪ force-off mode where force-off points can move depending on the demand of previous phases. Under this mode, non-coordinated phases can use unused time of previous phases. Fixed Force-offĪ force-off mode where force-off points cannot move. These points in a coordinated cycle ensure that the coordinated phases are provided a minimum amount of green time. Force-offĪ point within a cycle where a phase must end regardless of continued demand. Early Return to GreenĪ term used to describe the servicing of a coordinated phase in advance of its programmed begin time as a result of unused time from non-coordinated phases. Double CycleĪ cycle length that allows phases to be serviced twice as often as the other intersections in the coordinated system. The ability to synchronize multiple intersections to enhance the operation of one or more directional movements in a system. Additional terms can be found in the Glossary section of the Manual.
This section identifies and describes basic terminology used within this chapter. The intent of this chapter is to provide necessary background for the development of timing strategies. The third section provides guidelines for developing coordination timing plans, and the fourth section describes complexities associated with coordinated operations. The second section describes the concepts for coordination, its effect on time allocation, implementation issues, and time-space diagrams. The first section provides an overview of coordination including a summary of objectives, the fundamental concepts, and expectations of coordination timing. This chapter identifies coordination concepts using examples from research and practice. Examples include arterial streets, downtown networks, and closely spaced intersections such as diamond interchanges.
Coordination is a tool to provide the ability to synchronize multiple intersections to enhance the operation of one or more directional movements in a system. This chapter presents the concept of coordination of traffic signals. Figure 6-26 Time-Space Diagram Example of Early Return to Green.Figure 6-25 Vehicle trajectory diagrams showing the effect of changes in phase sequence.Figure 6-24 Loss of coordination due to pedestrian call.Figure 6-23 Non-coordinated phase operation with pedestrian timing exceeding phase split.Figure 6-22 Non-coordinated phase operation with pedestrian timing completed before the force-off for that phase.Figure 6-20 HCM Cycle Length Estimation.Figure 6-19 Webster’s Optimum Cycle Length.Figure 6-18 Quarter Cycle Offset Example Model.Figure 6-17 Alternating Offsets System of Intersections.Figure 6-16 Cycle Length & Theoretical Capacity.Figure 6-14 Daily Cycle Length Fluctuations.Figure 6-13 Time-Space Diagram Example of Benefits of Lagging Left Turns.Figure 6-12 Sequence of Left Turn Phasing as Shown in a Time-Space Diagram.Figure 6-11 Time-Space Diagram – Two-way Street Operation.Figure 6-10 Time-Space Diagram – One-Way Street Operation.Figure 6-9 Time-Space Diagram – Basic Concepts.Figure 6-8 Relationship between the Master Clock, Local Clock, and Offset.Figure 6-7 Standard Offset Reference Points for Type 170, NEMA TS1, and NEMA TS2 Controllers.Figure 6-6 Fixed and Floating Force-offs.Figure 6-4 Coordination using two rings.Figure 6-3 Example of coordination logic within one ring.Figure 6-2 Phase and ring-and-barrier diagrams of intersection of two one-way streets.Figure 6-1 Time-Space Diagram of a Coordinated Timing Plan.Table 6-1 Harmonic cycle lengths based on street classification in Harris County, Texas.6.6 Coordination Timing Plan Guidelines.6.5.1 Example Application of Time Based Coordination Transition.6.4.1 Basic Concepts (Time, Distance, Speed, and Delay).6.3.6 Pre-timed and Actuated Comparison.6.2 Principles of Coordinated Operation.