The topic of traffic signal design broadly includes any of an intersection's traffic signal control elements that have a physical presence at the intersection. The last section provides guidelines for selecting signal design values and choosing from among design options. The third section describes a procedure for determining appropriate signal design elements for a given intersection. The second section summarizes the basic concepts associated with key signal design elements. The first section provides an overview of the objectives of traffic signal design. The principles related to geometric design and operation are addressed in the Signalized Intersections: Informational Guide (1) The elements addressed in this Chapter include: signal control type, signal phasing, detection layout, and how the decisions made during traffic signal design affect signal timing for isolated (described in Chapter 5) and coordinated (described in Chapter 6) operation. This chapter documents the concepts of traffic signal design as they apply to traffic signal timing. Figure 4-20 Detector location for multiple detector technique (level approach).Figure 4-19 Distance to the beginning and end of the indecision zone.Figure 4-18 Indecision zone boundaries on a typical intersection approach. Figure 4-17 Example of vehicle detector design (through lane on side street).Figure 4-16 Examples of pedestrian push buttons.Figure 4-15 Phase diagram illustrating a right-turn overlap.Figure 4-14 Ring-barrier diagrams showing a leading pedestrian interval and an exclusive pedestrian phase4-19.Figure 4-13 Illustration of the yellow trap.Figure 4-12 Ring-and-barrier diagram showing protected lead-lag left turns.Figure 4-11 Guidelines for determining the potential need for a left-turn phase.Figure 4-10 Prohibited left turns by time of day.Figure 4-9 Ring-and-barrier diagram showing split phasing.Figure 4-8 Ring-and-barrier diagram showing protected-permissive phasing.Figure 4-7 Ring-and-barrier diagram showing protected phasing.Figure 4-6 Ring-and-barrier diagram showing permissive phasing.Figure 4-5 Ring-and-barrier diagram for intersection of two one-way streets.Figure 4-4 Standard ring-and-barrier diagram.Figure 4-3 Typical vehicular and pedestrian movements at a four-leg intersection.Figure 4-2 Phasing and movement diagram for the intersection of two one-way streets.Figure 4-1 Physical components of a signal system.Table 4-2 Recommended detector locations and timing settings for multiple detector technique.Table 4-1 Recommended distance between stop line and detector.4.7.5 Detection Design for Low-Speed Traffic Movements.4.7.4 Detection Design for High-Speed Approaches.4.4.3 Lead-Lag Left-Turn Phase Sequence.4.4.1 Lead-Lead Left-Turn Phase Sequence.4.3.6 Guidelines for Selecting Left-Turn Phasing.4.3.5 Prohibition of Left-Turns as a Phasing Option.4.3.3 Protected-Permissive Left-Turn Phasing.4.3.1 Permissive Only Left-Turn Phasing.4.1.1 Relationship between Signal Timing and Traffic Control Design.CHAPTER 4 TRAFFIC SIGNAL DESIGN TABLE OF CONTENTS
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