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iv Contents 1 Introduction .......................................................................................................................................... 1 1.1 Need for the Guidance .................................................................................................................. 1 1.2 Purpose of the Guidance .............................................................................................................. 2 1.3 Scope ............................................................................................................................................. 2 1.4 Guidance Development Process ................................................................................................... 3 2 Traffic Signal Phasing Concepts and Definitions ................................................................................... 5 2.1 Traffic Signal Basics ....................................................................................................................... 5 2.2 Signal Indications .......................................................................................................................... 7 2.3 Phase Mode .................................................................................................................................. 9 2.4 Phase Sequence .......................................................................................................................... 10 2.5 Yellow Trap .................................................................................................................................. 10 2.6 Actuation ..................................................................................................................................... 10 2.7 Right-turn Movements ................................................................................................................ 10 2.8 Pedestrian Phasing ...................................................................................................................... 10 2.9 Meaning of Acronyms and Abbreviations ................................................................................... 11 3 Traffic Signal Phasing Selection Process ............................................................................................. 12 3.1 Traffic Signal Phasing Selection Steps ......................................................................................... 12 3.2 Guidance Application .................................................................................................................. 16 4 Left-Turn Phasing Mode ...................................................................................................................... 17 4.1 Left-Turn Phasing Mode .............................................................................................................. 17 4.2 Left-Turn Phasing Mode Considerations ..................................................................................... 21 5 Right-Turn Phasing Mode ................................................................................................................... 32 5.1 Right-Turn Phasing Modes .......................................................................................................... 32 5.2 Right-Turn Phasing Considerations ............................................................................................. 33 5.3 Other Considerations .................................................................................................................. 38 6 Phase Sequence .................................................................................................................................. 39 6.1 Common Phase Sequences ......................................................................................................... 39 6.2 Phase Sequence Considerations ................................................................................................. 41 7 Pedestrian Phasing .............................................................................................................................. 47 7.1 Pedestrian Phasing Types ........................................................................................................... 47 7.2 Pedestrian Detection .................................................................................................................. 50 7.3 Two-Stage Crossing ..................................................................................................................... 51
v 8 Additional Signal Features .................................................................................................................. 53 8.1 Signal Cycle Length ...................................................................................................................... 53 8.2 Actuation (FHWA 2005) .............................................................................................................. 53 8.3 Coordination ............................................................................................................................... 54 9 Safety Considerations ......................................................................................................................... 55 9.1 Understanding the Safety Impacts Associated with Signal Phasing ........................................... 55 9.2 Methods of Safety Analysis ......................................................................................................... 55 9.3 New Research ............................................................................................................................. 57 10 Operations Considerations ............................................................................................................. 60 10.1 Operational Impacts Associated with Signal Phase Mode and Sequence .................................. 60 10.2 Methods of Operational Analysis ................................................................................................ 60 11 Combining Safety and Operations .................................................................................................. 62 11.1 Relationship ................................................................................................................................ 62 11.2 Overall Approach ........................................................................................................................ 62 11.3 Case Studies ................................................................................................................................ 65 References .................................................................................................................................................. 73
vi List of Figures Figure 1 - Breakdown of Agencies with and without Formal Policies for Signal Phasing ............................. 1 Figure 2 - Geometric Offset (Adapted from (FHWA 2009c) .......................................................................... 5 Figure 3 - Typical Traffic Signal Cycle ............................................................................................................ 6 Figure 4 - Depiction of Pedestrian Intervals (Source: FHWA 2009b) ............................................................ 6 Figure 5 - Components of a Traffic Signal ..................................................................................................... 7 Figure 6 - Traffic Signal Phasing Selection Process ..................................................................................... 12 Figure 7 - Typical Phasing Diagram for Permissive-Only Phasing (Adapted from NCHRP 2015) ................ 18 Figure 8 - Typical Phasing Diagram for Protected-Only Phasing (Adapted from NCHRP 2015) ................. 18 Figure 9 - Typical Phasing Diagram for Protected-Permissive Phasing (Adapted from NCHRP 2015) ........ 19 Figure 10 - Typical Phasing Diagram for Split Phasing on the Minor Street (Adapted from NCHRP 2015) 19 Figure 11 - Typical Phasing Diagram for Leading Left-Turn Sequence (Adapted from NCHRP 2015) ........ 40 Figure 12 - Typical Phasing Diagram for Lagging Left-Turn Sequence (Adapted from NCHRP 2015) ......... 40 Figure 13 - Typical Phasing Diagram for Lead-Lag Left-Turn Sequence (Adapted from NCHRP 2015) ....... 41 Figure 14 - Representation of Yellow Trap (Adapted from NCHRP 2003) .................................................. 42 Figure 15 - Limited Left-Turn Bay Storage Lengths (Adapted from NCHRP 2015) ...................................... 45 Figure 16 â Typical Phasing Diagram for Exclusive Pedestrian Movement (NCHRP 2008) ......................... 48 Figure 17 -Typical Phasing Diagram for Leading Pedestrian Interval (NCHRP 2008) .................................. 49 Figure 18 - Two-Stage Pedestrian Crossing ................................................................................................. 52 Figure 19 â Components of Phasing Decision ............................................................................................. 62 Figure 20 - Diagram of Case Study 1 ........................................................................................................... 66
vii List of Tables Table 1 - Left-Turn Signal Faces for Each Left-Turn Phasing Mode ............................................................ 20 Table 2 - Minimum Required Sight Distance for One Opposing Through Lane ......................................... 22 Table 3 - Critical Correctable Left-Turn Crash Counts ................................................................................. 25 Table 4 - Right-Turn Signal Faces for Each Right-Turn Phasing Mode ........................................................ 33 Table 5 - CMFs Derived from Research ....................................................................................................... 57 Table 6 - CMFs Derived from Research ....................................................................................................... 64 Table 7 - Recommended Unit Crash Costs (in 2016 dollars) ....................................................................... 64 Table 8 - Case Study 1a - Hourly Volume and Delay ................................................................................... 67 Table 9 - Case Study 1a - Annual Delay ....................................................................................................... 67 Table 10 - Case Study 1a - Annual Delay Cost ............................................................................................. 68 Table 11 - Case Study 1a - Annual Crash Estimation ................................................................................... 68 Table 12 - Case Study 1a - Annual Crash Cost ............................................................................................. 68 Table 13 - Case Study 1a - Annual Composite Cost .................................................................................... 69 Table 14 - Case Study 1b - Hourly Volume and Delay ................................................................................. 69 Table 15 - Case Study 1b - Annual Delay Cost ............................................................................................. 70 Table 16 - Case Study 1b - Annual Crash Cost ............................................................................................. 70 Table 17 - Case Study 1b - Annual Composite Cost .................................................................................... 70 Table 18 - Case Study 3 - Annual Delay Cost ............................................................................................... 71 Table 19 - Case Study 3 - Annual Crash Cost ............................................................................................... 71 Table 20 - Case Study 3 - Annual Composite Cost ...................................................................................... 72
viii Abstract This guide documents and presents the results of a study of traffic signal phasing. The guide synthesizes existing best practices as well as new information from the accompanying research effort (NCHRP 03- 118). This guide covers right-turn, left turn, and pedestrian phasing mode and sequence concepts. Concept definitions and best practices are provided for right-turn and pedestrian phasing mode and sequence. For left-turn phasing, this guide summarizes the concepts / existing best practices and includes additional information from the accompanying research effort (NCHRP 03-118). The guide presents safety performance functions (SPFs) and crash modification factors (CMFs) for left-turn phasing modes as well as charts to determine the operational impact of each phase mode. A methodology for combining the effect of safety and operations of the various left-turn phase modes is also provided in this guide.
