Signal Timing Manual - Second Edition (2015) / Chapter Skim
Currently Skimming:
Pages 75-107
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 75... ...
Chapter 5. Introducon to Timing Plans CHAPTER 5 INTRODUCTION TO TIMING PLANS CONTENTS 5.1 BASIC SIGNAL TIMING CONCEPTS ...................................................................................
|
From page 76... ...
Chapter 5. Introducon to Timing Plans LIST OF EXHIBITS Exhibit 5-1 Typical Movement and Phase Numbering (with Protected Left Turns)
|
From page 77... ...
Chapter 5. Introducon to Timing Plans 5-1 CHAPTER 5.
|
From page 78... ...
5-2 Chapter 5. Introduc
on to Timing Plans of the movements on an approach are assigned to one phase.
|
From page 79... ...
Chapter 5. Introducon to Timing Plans 5-3 o Phases 3 and 7 generally represent the minor street left-turn movements.
|
From page 80... ...
5-4 Chapter 5. Introduc
on to Timing Plans 5.1.2 Ring-and-Barrier Concept Rings and barriers fundamentally deine how a controller organizes phases, so that compatible phases can time together and conlicts do not occur.
|
From page 81... ...
Chapter 5. Introducon to Timing Plans 5-5 5.1.3 Le-Turn Phasing There are ive options for left-turn phasing at an intersection (summarized in Exhibit 5-4)
|
From page 82... ...
5-6 Chapter 5. Introduc
on to Timing Plans 5.1.3.1 Permied Le-Turn Phasing Permitted left-turn phasing is depicted in the ring-and-barrier diagram in Exhibit 5-5 and has the following characteristics: • Right-of-Way: Permitted phasing requires a user to yield to conlicting vehicular and pedestrian trafic before completing a left turn.
|
From page 83... ...
Chapter 5. Introducon to Timing Plans 5-7 • Challenges: The added left-turn phase increases the lost time within the cycle length and may increase delay for other movements.
|
From page 84... ...
5-8 Chapter 5. Introduc
on to Timing Plans a barrier.
|
From page 85... ...
Chapter 5. Introducon to Timing Plans 5-9 o One of the two approaches has a heavy volume, the other approach has minimal volume, and actuated control is used.
|
From page 86... ...
5-10 Chapter 5. Introducon to Timing Plans 5.1.3.6 Le-Turn Phase Sequence Regardless of the type of left-turn phasing that is applied, it may be advantageous under certain conditions to change the sequence in which left-turn phases are served (relative to the through phases)
|
From page 87... ...
Chapter 5. Introducon to Timing Plans 5-11 Opposing left turns can also run in a lead-lag sequence, where they begin and end at different times relative to the through phases (as shown by Phases 1 and 5 in Exhibit 5-10)
|
From page 88... ...
5-12 Chapter 5. Introducon to Timing Plans Overlaps can be used to combine phases for any non-con licting movements, but they are most often used for right-turn movements where exclusive right-turn lanes exist.
|
From page 89... ...
Chapter 5. Introducon to Timing Plans 5-13 1 Movement Number Overlap Leer1 Parent Phase Pedestrian Modifier Phase for Right-Turn Overlap Omit (If Available)
|
From page 90... ...
5-14 Chapter 5. Introducon to Timing Plans pedestrian phase is called, the adjacent right-turn movement will be permitted (i.e., green ball)
|
From page 91... ...
5-14 Chapter 5. Introducon to Timing Plans pedestrian phase is called, the adjacent right-turn movement will be permitted (i.e., green ball)
|
From page 92... ...
5-16 Chapter 5. Introducon to Timing Plans 5.1.5 Detector Assignments Detector assignments deine how the controller will react when detector inputs are received from the ield.
|
From page 93... ...
Chapter 5. Introducon to Timing Plans 5-17 Phase Detector Number1 Func
on Vehicle Phase 1 1 Call & Extend Vehicle Phase 2 2 Call & Extend Vehicle Phase 2 12 Call Vehicle Phase 3 3 Call & Extend Vehicle Phase 4 4 Call & Extend Vehicle Phase 4 14 Call Vehicle Phase 5 5 Call & Extend Vehicle Phase 6 6 Call & Extend Vehicle Phase 6 16 Call Vehicle Phase 7 7 Call & Extend Vehicle Phase 8 8 Call & Extend Vehicle Phase 8 18 Call 1 Detector number will vary depending on field wiring.
|
From page 94... ...
5-18 Chapter 5. Introducon to Timing Plans Phase / Overlap Load Switch Number Vehicle Phase 1 1 Vehicle Phase 2 2 Vehicle Phase 3 3 Vehicle Phase 4 4 Vehicle Phase 5 5 Vehicle Phase 6 6 Vehicle Phase 7 7 Vehicle Phase 8 8 Overlap A 9 Overlap B 10 Overlap C 11 Overlap D 12 Pedestrian Phase 2 + FYA1*
|
From page 95... ...
Chapter 5. Introducon to Timing Plans 5-19 5.2 CRITICAL MOVEMENT ANALYSIS An important principle behind effective signal timing plans is the relationship between signal timing, phasing, and the capacity of an intersection.
|
From page 96... ...
5-20 Chapter 5. Introducon to Timing Plans 5.2.1 Step 1: Record Demand Volumes The irst step in the critical movement analysis procedure is determining peak period volumes in each lane at the intersection (as shown in Exhibit 5-20 and Exhibit 5-21)
|
From page 97... ...
Chapter 5. Introducon to Timing Plans 5-21 5.2.2 Step 2: Determine Crical Phase Pairs The cycle length needed to accommodate all of the vehicles at an intersection can be estimated by identifying the movements that require the most time (the critical movements)
|
From page 98... ...
5-22 Chapter 5. Introduc
on to Timing Plans In Example #1, Phases 1 and 2 have more con licting volume than Phases 5 and 6 (as depicted in Exhibit 5-24)
|
From page 99... ...
Chapter 5. Introducon to Timing Plans 5-23 approach (Phase 4)
|
From page 100... ...
5-24 Chapter 5. Introducon to Timing Plans vehicles from the other approach will proceed through the intersection.
|
From page 101... ...
Chapter 5. Introducon to Timing Plans 5-25 5.2.4 Step 4: Esmate the Cycle Length The critical volume at an intersection can be used to estimate the required cycle length.
|
From page 102... ...
5-26 Chapter 5. Introducon to Timing Plans longer cycle length may be appropriate to favor major street traf ic.
|
From page 103... ...
Chapter 5. Introducon to Timing Plans 5-27 5.3.1.1 Determinisc or Equaon-Based Models For many practitioners, deterministic or equation-based models are the models of choice when developing signal timing plans, particularly for coordinated systems.
|
From page 104... ...
5-28 Chapter 5. Introducon to Timing Plans algorithms to replace the approximation used in simulation models, more accurately re lecting how a controller will operate.
|
From page 105... ...
Chapter 5. Introducon to Timing Plans 5-29 features, and required ield calibration should be taken into account when choosing a software tool.
|
From page 106... ...
5-30 Chapter 5. Introducon to Timing Plans time.
|
From page 107... ...
5-30 Chapter 5. Introducon to Timing Plans time.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.