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Signal Timing Manual - Second Edition (2015)

Chapter: Chapter 6 - Intersection/Uncoordinated Timing

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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Suggested Citation:"Chapter 6 - Intersection/Uncoordinated Timing ." National Academies of Sciences, Engineering, and Medicine. 2015. Signal Timing Manual - Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22097.
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Chapter 6. Intersecon/Uncoordinated Timing CHAPTER 6 INTERSECTION/UNCOORDINATED TIMING CONTENTS 6.1 BASIC SIGNAL TIMING PARAMETERS ............................................................................ 6-1 6.1.1 Yellow Change ............................................................................................................................ 6-2 6.1.2 Red Clearance ............................................................................................................................. 6-4 6.1.3 Minimum Green ......................................................................................................................... 6-5 6.1.4 Maximum Green ........................................................................................................................ 6-8 6.1.5 Passage Time (Unit Extension or Gap Time) ............................................................... 6-10 6.1.6 Pedestrian Intervals ............................................................................................................... 6-16 6.1.7 Dual Entry .................................................................................................................................. 6-20 6.1.8 Recalls and Memory Modes ................................................................................................ 6-20 6.2 DETECTOR CONFIGURATIONS ........................................................................................ 6-23 6.2.1 Delay ............................................................................................................................................. 6-23 6.2.2 Extend Time (Carry-Over or Stretch Time) ................................................................. 6-25 6.2.3 Detector Switching ................................................................................................................. 6-27 6.3 TIME-OF-DAY PLANS .......................................................................................................... 6-27 6.4 REFERENCES ................................................................................................................ ........ 6-28 Signal Timing Manual, Second Edion

Chapter 6. Intersecon/Uncoordinated Timing LIST OF EXHIBITS Exhibit 6-1 Basic Signal Timing Parameter Guidance ........................................................... 6-1 Exhibit 6-2 Duration of Minimum Yellow Change Interval ................................................. 6-4 Exhibit 6-3 Red Clearance Interval................................................................................................ 6-5 Exhibit 6-4 Typical Values for Minimum Green to Satisfy Driver Expectancy ............ 6-6 Exhibit 6-5 Typical Variable Initial Timing Values for Setback Detection Queue Clearance (Without Stop Bar Detection) .............................................. 6-7 Exhibit 6-6 Variable Initial ................................................................................................................ 6-7 Exhibit 6-7 Typical Values for Minimum Phase Length for Bicycle Timing ................. 6-8 Exhibit 6-8 Maximum Green ............................................................................................................ 6-9 Exhibit 6-9 Typical Values for Maximum Green Based on Facility Type .................... 6-10 Exhibit 6-10 Passage Time ............................................................................................................... 6-11 Exhibit 6-11 Passage Time and Flow Rate Relationship ...................................................... 6-12 Exhibit 6-12 Typical Values for Passage Time ......................................................................... 6-14 Exhibit 6-13 Relationship between Passage Time, Minimum Gap, Time before Reduction, and Time to Reduce ........................................................................... 6-15 Exhibit 6-14 Gap Reduction Features and Flow Rate Relationship ................................. 6-16 Exhibit 6-15 Pedestrian Intervals .................................................................................................. 6-17 Exhibit 6-16 Typical Values for Pedestrian Walk Interval .................................................. 6-18 Exhibit 6-17 Example of Extended Push Button Press Function Signage ..................... 6-18 Exhibit 6-18 Calculated Values for Pedestrian Clearance Time (Based on a Walking Speed of 3.5 Feet per Second) ............................................................ 6-19 Exhibit 6-19 Pedestrian Interval Requirements Based on Walking Speed .................. 6-19 Exhibit 6-20 Leading Pedestrian Intervals ................................................................................ 6-20 Exhibit 6-21 Recall and Memory Mode Considerations ....................................................... 6-22 Exhibit 6-22 Typical Settings on Recalls and Memory Modes at a Fully- Actuated Intersection ............................................................................................... 6-22 Exhibit 6-23 Delay Timer .................................................................................................................. 6-24 Exhibit 6-24 Typical Values for Delay .......................................................................................... 6-25 Exhibit 6-25 Extend Timer ............................................................................................................... 6-26 Exhibit 6-26 Typical Settings for Detector Switching under Protected- Permitted Operations ............................................................................................... 6-27 Signal Timing Manual, Second Edion

Chapter 6. Intersecon/Uncoordinated Timing 6-1 CHAPTER 6. INTERSECTION/UNCOORDINATED TIMING Chapter 6 provides guidance on basic signal timing parameters used at uncoordinated intersections (i.e., intersections running in “free” operation). Using the typical timing values in this chapter, a practitioner should be able to develop timing plans for a standard eight-phase intersection (without collecting extensive data or conducting extensive analysis). These timing parameters also apply when the controller is being coordinated with other intersections, but additional parameters, discussed in Chapter 7, must also be selected for coordinated operations. 6.1 BASIC SIGNAL TIMING PARAMETERS Several basic timing parameters are typically programmed for each phase at a signalized intersection (i.e., associated with the signal controller phase table), including • Yellow change, • Red clearance, • Minimum green, • Maximum green, • Passage time (unit extension or gap time), • Pedestrian intervals, • Dual entry, and • Recalls and memory modes. This chapter includes descriptions of these parameters and their functions, as well as some direction for a practitioner to use as he or she chooses speci„ic values. This guidance was developed assuming an eight-phase intersection with (1) full actuation for vehicles and pedestrians and (2) presence mode detection (discussed in detail in Section 6.2). Exhibit 6-1 provides a summary of the consequences associated with giving too much or too little time to a parameter, as well as the variables that should affect the ultimate parameter value that is chosen. Timing Parameter Consequence for Too Lile Time Consequence for Too Much Time Dependent On Variables Including: S ec o n 6. 1. 1 Yellow Change □ May create a dilemma zone (Type I) □ May cause a higher frequency of red-light running □ May encourage disrespect by familiar drivers □ Driver percepon- reacon me □ Vehicle deceleraon rate □ Vehicle approach speed □ Approach grade Se c on 6. 1. 2 Red Clearance □ Potenal conflict aƒer phase begins □ Wasted me at the intersecon □ Intersecon width □ Vehicle length □ Vehicle approach speed The signal controller phase table contains signal ming parameter values associated with specific phases. “Interval” is a term that describes the me when a signal indicaon does not change (e.g., walk, flashing don’t walk, or green interval). Exhibit 6-1 Basic Signal Timing Parameter Guidance Signal Timing Manual, Second Edion

Signal Timing Manual, Second Edion 6-2 Chapter 6. Intersecon/Uncoordinated Timing Timing Parameter Consequence for Too Lile Time Consequence for Too Much Time Dependent On Variables Including: Se c on 6. 1. 3 Minimum Green □ May violate driver expectaons (leading to a possible increase in rear-end crashes) □ May not accommodate pedestrian needs □ May not accommodate bicycle needs □ Wasted me at the intersecon □ Driver expectancy □ Detector locaons □ Number of queued vehicles □ Pedestrian intervals □ Bicycle speed and acceleraon Se c on 6. 1. 4 Maximum Green □ Some vehicles may not be served because the phase capacity is inadequate for demand □ Wasted me at the intersecon (parcularly if there is broken detecon) □ Possible queuing on movements with long delays □ Vehicle demand □ Intersecon capacity Se c on 6. 1. 5 Passage Time (Unit Extension or Gap Time) □ Green may end prematurely before all vehicles have been served □ Delays to other movements caused by extension of the phase □ Detecon design □ Detecon mode □ Vehicle approach speed Se c on 6. 1. 6 Walk □ May not accommodate high volumes of pedestrians □ Wasted me at the intersecon □ Pedestrian volumes □ Push buƒon locaons □ Pedestrian crossing distance □ Pedestrian walking speed Flashing Don’t Walk (FDW) □ May not accommodate the me needed for pedestrians to cross the street □ Wasted me at the intersecon □ Pedestrian crossing distance □ Pedestrian walking speed 6.1.1 Yellow Change The yellow change interval warns users that there is about to be a change in right- of-way assignment at the intersection. 6.1.1.1 Operang Environment Consideraons for Yellow Change A state’s vehicle code its into one of two broad categories—permissive or restrictive yellow law—described below: • Permissive Yellow Law: Vehicular trafic facing a steady circular yellow or yellow arrow signal is thereby warned that the related green movement is being terminated or that a red indication will be exhibited immediately thereafter. This rule comes from paragraph 11-202 of the Uniform Vehicle Code (1). • Restrictive Yellow Law: These laws, which are less common, require stopping unless not safe to do so. An adequate yellow interval should allow vehicles to stop.

Signal Timing Manual, Second Edion 6-2 Chapter 6. Intersecon/Uncoordinated Timing Timing Parameter Consequence for Too Lile Time Consequence for Too Much Time Dependent On Variables Including: Se c on 6. 1. 3 Minimum Green □ May violate driver expectaons (leading to a possible increase in rear-end crashes) □ May not accommodate pedestrian needs □ May not accommodate bicycle needs □ Wasted me at the intersecon □ Driver expectancy □ Detector locaons □ Number of queued vehicles □ Pedestrian intervals □ Bicycle speed and acceleraon Se c on 6. 1. 4 Maximum Green □ Some vehicles may not be served because the phase capacity is inadequate for demand □ Wasted me at the intersecon (parcularly if there is broken detecon) □ Possible queuing on movements with long delays □ Vehicle demand □ Intersecon capacity Se c on 6. 1. 5 Passage Time (Unit Extension or Gap Time) □ Green may end prematurely before all vehicles have been served □ Delays to other movements caused by extension of the phase □ Detecon design □ Detecon mode □ Vehicle approach speed Se c on 6. 1. 6 Walk □ May not accommodate high volumes of pedestrians □ Wasted me at the intersecon □ Pedestrian volumes □ Push buƒon locaons □ Pedestrian crossing distance □ Pedestrian walking speed Flashing Don’t Walk (FDW) □ May not accommodate the me needed for pedestrians to cross the street □ Wasted me at the intersecon □ Pedestrian crossing distance □ Pedestrian walking speed 6.1.1 Yellow Change The yellow change interval warns users that there is about to be a change in right- of-way assignment at the intersection. 6.1.1.1 Operang Environment Consideraons for Yellow Change A state’s vehicle code its into one of two broad categories—permissive or restrictive yellow law—described below: • Permissive Yellow Law: Vehicular trafic facing a steady circular yellow or yellow arrow signal is thereby warned that the related green movement is being terminated or that a red indication will be exhibited immediately thereafter. This rule comes from paragraph 11-202 of the Uniform Vehicle Code (1). • Restrictive Yellow Law: These laws, which are less common, require stopping unless not safe to do so. An adequate yellow interval should allow vehicles to stop. Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-3 Because of the various interpretations of the yellow change interval, practitioners are encouraged to refer to local and regional statutes for guidance when determining the purpose of yellow change time. 6.1.1.2 Typical Values for Yellow Change The Manual on Uniform Trafic Control Devices (2) requires that the duration of the yellow change interval be determined using engineering practices. These should be based on individual intersection conditions (i.e., approach speed). The yellow change interval should last approximately 3 to 6 seconds, with longer intervals being used on higher speed approaches. The Institute of Transportation Engineers (ITE) offers Equation 6-1 for computing the yellow change interval (3). The equation calculates the time required for a driver to make a decision to come to a safe stop or proceed. This is the minimum time to eliminate a dilemma zone (Type I), which exists if the yellow is too short. Decision zones (also known as Type II dilemma zones or indecision zones), which are related to detection design, are discussed in detail in Chapter 4. where Y = yellow change interval (seconds), t = perception-reaction time to the onset of a yellow indication (seconds), v = approach speed (miles per hour [mph]), a = deceleration rate in response to the onset of a yellow indication (feet per second per second), and g = grade, with uphill positive and downhill negative (percent grade/100) (feet/feet). Although values will vary by user population and local conditions, a perception- reaction time (t) of 1.0 second and a deceleration rate (a) of 10 feet per second per second are often cited for use in Equation 6-1 (4, 5) and have recently been recommended for use in NCHRP 731 (6). These recommended values are different from those cited in highway geometric design policy documents because they are based on driver response to the yellow indication, which is an expected condition. They are not based on the longer reaction time necessary for an unexpected (or surprise) condition. When applying Equation 6-1 to through movement phases, the speed used is generally either the 85th-percentile speed or the posted regulatory speed limit, depending on agency policy (7). When applying Equation 6-1 to left-turn phases, the speed can equal that of the adjacent through movement, but it can also be slower, as left-turning drivers inherently slow to a comfortable turning speed. Exhibit 6-2 shows minimum yellow change interval results based on Equation 6-1 and the recommended values discussed above. These values for minimum yellow are long enough to prevent a dilemma zone, so drivers will not ‘ind themselves in an area where they can neither enter on yellow nor stop. This is the minimum yellow required to prevent a vehicle from entering on red when, in fact, the driver might not have had enough time to stop. It is very desirable for drivers in a region to see a consistent applicaon of the yellow change interval. Equaon 6-1

Signal Timing Manual, Second Edion 6-4 Chapter 6. Intersecon/Uncoordinated Timing The values for the yellow change interval in Exhibit 6-2 are based on negligible approach grades. They should be increased by 0.1 second for every 1 percent of downgrade. Similarly, they should be decreased by 0.1 second for every 1 percent of upgrade. To illustrate, consider an approach with a 30 mph approach speed and 4- percent downgrade. The estimated yellow change period should be 3.6 seconds (= 3.2 + (0.1 × 4)). Approach Speed (MPH) Minimum Yellow Change1 (Seconds) 25 3.0* 30 3.2 35 3.6 40 3.9 45 4.3 50 4.7 55 5.0 60 5.4 1 Based on negligible approach grades. Adjustments are required for upgrades and downgrades. * The MUTCD (2) recommends a minimum duration of 3 seconds for the yellow change interval. 6.1.2 Red Clearance The red clearance interval is an optional signal timing parameter that provides a period at the end of the yellow change interval, during which the phase has a red signal display before the display of green for the following phase. The purpose of this interval is to allow time for vehicles that entered the intersection during the yellow change interval to reach an appropriate location prior to the next phase. Practitioners should understand that site-speciƒic conditions, such as heavy vehicles and downgrades, may warrant special attention. 6.1.2.1 Operang Environment Consideraons for Red Clearance The use of a red clearance interval is optional, and there is no consensus on its application or duration. Recent research indicates that the use of a red clearance interval shows some reduction of red-light-running violations. In these studies, there was also a signiƒicant reduction in right-angle crashes after implementing a red clearance interval. However, other research suggests that this reduction may only be temporary. A comprehensive study of long-term effects for the Minnesota Department of Transportation (8) indicated short-term reductions in crash rates were achieved (approximately one year after the implementation), but long-term reductions were not observed, which implies that there may not be safety beneƒits associated with increased red clearance intervals. A disadvantage of using the red clearance interval is that there is a reduction in available green time for other phases. At intersections where the timing for minor movements is restricted (e.g., under coordinated operations, which are explained in Chapter 7), the extra time for a red clearance interval comes from the remaining phases at the intersection. In cases where major movements are already at or near saturation, the reduction in capacity associated with providing red clearance intervals should be accounted for in an operational analysis. Recent research associated with NCHRP 731 (6) has conƒirmed that vehicles do not enter an intersection until 1 second after the start of green and recommends red Exhibit 6-2 Duraon of Minimum Yellow Change Interval Some publicaons incorrectly refer to the red clearance interval as an all-red interval. Red clearance only applies to a single phase.

Signal Timing Manual, Second Edion 6-4 Chapter 6. Intersecon/Uncoordinated Timing The values for the yellow change interval in Exhibit 6-2 are based on negligible approach grades. They should be increased by 0.1 second for every 1 percent of downgrade. Similarly, they should be decreased by 0.1 second for every 1 percent of upgrade. To illustrate, consider an approach with a 30 mph approach speed and 4- percent downgrade. The estimated yellow change period should be 3.6 seconds (= 3.2 + (0.1 × 4)). Approach Speed (MPH) Minimum Yellow Change1 (Seconds) 25 3.0* 30 3.2 35 3.6 40 3.9 45 4.3 50 4.7 55 5.0 60 5.4 1 Based on negligible approach grades. Adjustments are required for upgrades and downgrades. * The MUTCD (2) recommends a minimum duration of 3 seconds for the yellow change interval. 6.1.2 Red Clearance The red clearance interval is an optional signal timing parameter that provides a period at the end of the yellow change interval, during which the phase has a red signal display before the display of green for the following phase. The purpose of this interval is to allow time for vehicles that entered the intersection during the yellow change interval to reach an appropriate location prior to the next phase. Practitioners should understand that site-speciƒic conditions, such as heavy vehicles and downgrades, may warrant special attention. 6.1.2.1 Operang Environment Consideraons for Red Clearance The use of a red clearance interval is optional, and there is no consensus on its application or duration. Recent research indicates that the use of a red clearance interval shows some reduction of red-light-running violations. In these studies, there was also a signiƒicant reduction in right-angle crashes after implementing a red clearance interval. However, other research suggests that this reduction may only be temporary. A comprehensive study of long-term effects for the Minnesota Department of Transportation (8) indicated short-term reductions in crash rates were achieved (approximately one year after the implementation), but long-term reductions were not observed, which implies that there may not be safety beneƒits associated with increased red clearance intervals. A disadvantage of using the red clearance interval is that there is a reduction in available green time for other phases. At intersections where the timing for minor movements is restricted (e.g., under coordinated operations, which are explained in Chapter 7), the extra time for a red clearance interval comes from the remaining phases at the intersection. In cases where major movements are already at or near saturation, the reduction in capacity associated with providing red clearance intervals should be accounted for in an operational analysis. Recent research associated with NCHRP 731 (6) has conƒirmed that vehicles do not enter an intersection until 1 second after the start of green and recommends red Exhibit 6-2 Duraon of Minimum Yellow Change Interval Some publicaons incorrectly refer to the red clearance interval as an all-red interval. Red clearance only applies to a single phase. Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-5 clearance intervals as shown in Exhibit 6-3. (The width of the intersection is measured from the stop bar to the extension of the cross-street curb line or the outside edge of the farthest cross-street travel lane.) Some modern controllers can be conigured to implement a red clearance extension when a vehicle is detected to be in an undesirable position at the onset of a conlicting green. This application is consistent with MUTCD guidance that allows lengthening of the red clearance interval. Approach Speed (MPH) Red Clearance1 (Seconds) Width of Intersecon (Feet) 30 50 70 90 110 25 0.4 0.9 1.5 2.0 2.5 30 0.1 0.6 1.0 1.5 2.0 35 0.0 0.4 0.8 1.1 1.5 40 0.0 0.2 0.5 0.9 1.2 45 0.0 0.1 0.4 0.7 1.0 50 0.0 0.0 0.2 0.5 0.8 55 0.0 0.0 0.1 0.4 0.6 60 0.0 0.0 0.0 0.2 0.5 1 Based on recent research reported in NCHRP 731 (6), the calculated red clearance values have been reduced by 1 second. 6.1.3 Minimum Green The minimum green parameter represents the least amount of time that a green signal indication will be displayed for a phase. Minimum green should be set to meet driver expectations, but its duration may also be based on considerations of queue length or pedestrian timing. High-speed rural locations, especially those with high truck volumes, may beneit from longer times than those at typical urban intersections. A minimum green that is too long may result in increased delay and excessive queues at an intersection; one that is too short may violate driver expectations or, in some cases, pedestrian needs. (In this chapter, pedestrian detection and indications are assumed to be present. Pedestrian timing considerations are discussed in detail in Section 6.1.6.) 6.1.3.1 Operang Environment Consideraons for Minimum Green Vehicles that have longer start-up times (such as bicycles, trucks, and transit) generally require more time to clear queues at the beginning of the green interval. Longer minimum green times may be appropriate at locations with high numbers of these types of vehicles, depending on the type of detection design. 6.1.3.2 Typical Values for Minimum Green Based on Driver Expectancy The recommended duration of minimum green needed to satisfy driver expectancy varies among practitioners. Some use 15 seconds or more of minimum green; other practitioners use as little as 2 seconds. If a minimum green parameter is set too low and violates driver expectancy, there is a risk of increased rear-end crashes. The values listed in Exhibit 6-4 are typical for the speciied combinations of phase and facility type. Exhibit 6-3 Red Clearance Interval

Signal Timing Manual, Second Edion 6-6 Chapter 6. Intersecon/Uncoordinated Timing Phase Type Facility Type Minimum Green (Seconds) Through Major Arterial (> 40 mph) 10 to 15 Major Arterial (≤ 40 mph) 7 to 15 Minor Arterial 4 to 10 Collector, Local, or Driveway 2 to 10 Le‡ Turn Any 2 to 5 6.1.3.3 Typical Values for Minimum Green Based on Queue Clearance In addition to driver expectancy, the duration of minimum green can also be inluenced by the location of detectors. If stop bar detection is not present, a minimum green interval is needed to clear the vehicles queued between the stop bar and the nearest setback detector. If the minimum green is not long enough to clear the vehicles, a vehicle might get “stuck” between the setback detector and the stop bar. Without stop bar detection, the controller will not know that there is a vehicle waiting. Equation 6-2 (in combination with Equation 6-3) can be used to estimate the minimum green needed to satisfy queue clearance. Equation 6-2 assumes a start-up lost time of 3 seconds and that each subsequent vehicle requires 2 seconds to clear the intersection: where Gq = minimum green duration for queue clearance (seconds) and n = number of vehicles between stop bar and nearest setback detector in one lane. where d = distance between the stop bar and the downstream edge of the nearest setback detector (feet) and Lv = length of vehicle (feet), set at 25 feet. Modern controllers can adjust the amount of green time given to a phase based on queue length (when stop bar detection is not used) using a parameter called “variable initial.” The minimum green to satisfy driver expectancy (discussed in the previous section) is often used to deine the lower limit for variable initial, and the maximum value is deined by the green time needed for queue clearance (provided it is higher than the minimum green required for driver expectancy). Variable initial will be increased incrementally based on the number of actuations (i.e., number of users being detected) during the yellow and red intervals until the upper limit is reached, but will never be less than the minimum green. Exhibit 6-5 provides some typical values for minimum green, maximum variable initial, and seconds added per actuation, while Exhibit 6-6 illustrates the concept. Note that the green time for queue clearance (calculated using Equation 6-2) is noted in Exhibit 6-5 as maximum variable initial. Exhibit 6-4 Typical Values for Minimum Green to Sasfy Driver Expectancy As described in Chapter 5, start-up lost me is the me used by the first few vehicles in a queue to react to the green indicaon and accelerate. Equaon 6-2 Equaon 6-3

Signal Timing Manual, Second Edion 6-6 Chapter 6. Intersecon/Uncoordinated Timing Phase Type Facility Type Minimum Green (Seconds) Through Major Arterial (> 40 mph) 10 to 15 Major Arterial (≤ 40 mph) 7 to 15 Minor Arterial 4 to 10 Collector, Local, or Driveway 2 to 10 Le‡ Turn Any 2 to 5 6.1.3.3 Typical Values for Minimum Green Based on Queue Clearance In addition to driver expectancy, the duration of minimum green can also be inluenced by the location of detectors. If stop bar detection is not present, a minimum green interval is needed to clear the vehicles queued between the stop bar and the nearest setback detector. If the minimum green is not long enough to clear the vehicles, a vehicle might get “stuck” between the setback detector and the stop bar. Without stop bar detection, the controller will not know that there is a vehicle waiting. Equation 6-2 (in combination with Equation 6-3) can be used to estimate the minimum green needed to satisfy queue clearance. Equation 6-2 assumes a start-up lost time of 3 seconds and that each subsequent vehicle requires 2 seconds to clear the intersection: where Gq = minimum green duration for queue clearance (seconds) and n = number of vehicles between stop bar and nearest setback detector in one lane. where d = distance between the stop bar and the downstream edge of the nearest setback detector (feet) and Lv = length of vehicle (feet), set at 25 feet. Modern controllers can adjust the amount of green time given to a phase based on queue length (when stop bar detection is not used) using a parameter called “variable initial.” The minimum green to satisfy driver expectancy (discussed in the previous section) is often used to deine the lower limit for variable initial, and the maximum value is deined by the green time needed for queue clearance (provided it is higher than the minimum green required for driver expectancy). Variable initial will be increased incrementally based on the number of actuations (i.e., number of users being detected) during the yellow and red intervals until the upper limit is reached, but will never be less than the minimum green. Exhibit 6-5 provides some typical values for minimum green, maximum variable initial, and seconds added per actuation, while Exhibit 6-6 illustrates the concept. Note that the green time for queue clearance (calculated using Equation 6-2) is noted in Exhibit 6-5 as maximum variable initial. Exhibit 6-4 Typical Values for Minimum Green to Sasfy Driver Expectancy As described in Chapter 5, start-up lost me is the me used by the first few vehicles in a queue to react to the green indicaon and accelerate. Equaon 6-2 Equaon 6-3 Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-7 Distance Between Stop Bar and Nearest Setback Detector (Feet) Minimum Green (Seconds) Maximum Variable Inial (Seconds) Seconds Added per Actuaon1 275 10 25 2.0 350 10 31 2.0 425 10 37 2.0 500 10 43 2.0 1 Seconds added per actuation assumes approximately 2-second headways. 6.1.3.4 Typical Values for Minimum Green Based on Bicycle Timing At intersections with signiicant bicycle volumes and stop bar detection for bicycles, the minimum green time (along with the yellow change and red clearance intervals) should accommodate a bicycle crossing the intersection. A practitioner does not generally need to accommodate a bicycle solely within the minimum green time. Instead, bicycles should be accommodated within a minimum phase length (that includes a minimum green time, yellow change interval, and red clearance interval). Equation 6-4, provided by the California Department of Transportation’s (Caltrans) California Manual on Uniform Trafic Control Devices (9), can be used to calculate the minimum amount of time required for a bicycle to clear an intersection. Exhibit 6-5 Typical Variable Inial Timing Values for Setback Detecon Queue Clearance (Without Stop Bar Detecon) Exhibit 6-6 Variable Inial

Signal Timing Manual, Second Edion 6-8 Chapter 6. Intersecon/Uncoordinated Timing where Gmin = length of minimum green interval (seconds), Y = length of yellow change interval (seconds), Rclear = length of red clearance interval (seconds), and w = distance from limit line to far side of last conlicting lane (feet). A bicycle crossing speed of 10 miles per hour (14.7 feet per second) is assumed in the equation, and an effective start-up lost time of 6 seconds is used to represent the time lost to reacting to the green indication and then accelerating to full speed. Typical values for the minimum phase length used in a bicycle environment are provided in Exhibit 6-7. Bicycle Crossing Distance (Distance from Limit Line to Far Side of Last Conflicng Lane) (Feet) Minimum Phase Length (Seconds) 40 9.1 50 9.8 60 10.5 70 11.2 80 11.9 90 12.5 100 13.2 110 13.9 120 14.6 130 15.3 140 15.9 150 16.6 160 17.3 170 18.0 180 18.7 6.1.4 Maximum Green The maximum green parameter represents the maximum amount of time that a green signal indication can be displayed in the presence of a call on a conlicting phase. A maximum green that is too long may result in wasted time at an intersection, and movements that experience long delays as a result could experience queuing. If the maximum green value is too short, then the phase capacity may be inadequate for the trafic demand, and some vehicles will remain unserved at the end of the green interval. As shown in Exhibit 6-8, the maximum green timer begins timing upon the presence of a conlicting call. If there is demand on the phase that is currently timing and there are no conlicting calls, the maximum green timer will be reset to its maximum value until an opposing call occurs. Maximum green is used to limit the delay to any movement at an intersection and keeps the cycle length to a desired maximum amount. It also guards against long green times due to continuous demand or broken detectors. The normal failure mode of a detector is to place a continuous call for service, so a failed detector on a phase will cause that phase’s maximum green to time every cycle. Therefore, setting a proper Equaon 6-4 Exhibit 6-7 Typical Values for Minimum Phase Length for Bicycle Timing “Call” is a term used to describe the presence of vehicles or pedestrians at detectors. When a phase terminates at its maximum green me (instead of during a gap in traffic), the phase is considered to have “maxed out.”

Signal Timing Manual, Second Edion 6-8 Chapter 6. Intersecon/Uncoordinated Timing where Gmin = length of minimum green interval (seconds), Y = length of yellow change interval (seconds), Rclear = length of red clearance interval (seconds), and w = distance from limit line to far side of last conlicting lane (feet). A bicycle crossing speed of 10 miles per hour (14.7 feet per second) is assumed in the equation, and an effective start-up lost time of 6 seconds is used to represent the time lost to reacting to the green indication and then accelerating to full speed. Typical values for the minimum phase length used in a bicycle environment are provided in Exhibit 6-7. Bicycle Crossing Distance (Distance from Limit Line to Far Side of Last Conflicng Lane) (Feet) Minimum Phase Length (Seconds) 40 9.1 50 9.8 60 10.5 70 11.2 80 11.9 90 12.5 100 13.2 110 13.9 120 14.6 130 15.3 140 15.9 150 16.6 160 17.3 170 18.0 180 18.7 6.1.4 Maximum Green The maximum green parameter represents the maximum amount of time that a green signal indication can be displayed in the presence of a call on a conlicting phase. A maximum green that is too long may result in wasted time at an intersection, and movements that experience long delays as a result could experience queuing. If the maximum green value is too short, then the phase capacity may be inadequate for the trafic demand, and some vehicles will remain unserved at the end of the green interval. As shown in Exhibit 6-8, the maximum green timer begins timing upon the presence of a conlicting call. If there is demand on the phase that is currently timing and there are no conlicting calls, the maximum green timer will be reset to its maximum value until an opposing call occurs. Maximum green is used to limit the delay to any movement at an intersection and keeps the cycle length to a desired maximum amount. It also guards against long green times due to continuous demand or broken detectors. The normal failure mode of a detector is to place a continuous call for service, so a failed detector on a phase will cause that phase’s maximum green to time every cycle. Therefore, setting a proper Equaon 6-4 Exhibit 6-7 Typical Values for Minimum Phase Length for Bicycle Timing “Call” is a term used to describe the presence of vehicles or pedestrians at detectors. When a phase terminates at its maximum green me (instead of during a gap in traffic), the phase is considered to have “maxed out.” Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-9 maximum green duration could potentially minimize the impact to traf ic in case of detector failure. Ideally, the maximum green will not be reached because the detection system will ind a gap to end the phase (discussed in detail in Section 6.1.5). However, if there are continuous calls for service on the current phase and a call on one or more con licting phases, the maximum green parameter will eventually terminate the current phase. 6.1.4.1 Operang Environment Consideraons for Maximum Green The maximum green value is typically developed based on traf ic volumes and does not generally change with different operating environment characteristics. One exception is on residential minor streets where long maximum greens might encourage cut-through traf ic. 6.1.4.2 Typical Values for Maximum Green The maximum green value should exceed the green duration needed to serve the typical maximum queue and, thereby, allow the phase to accommodate cycle-to-cycle peaks in demand. A properly timed maximum green duration will commonly result in frequent phase termination by gap out (where a gap in traf ic, indicating inef icient low, results in the end of a phase) during low-to-moderate volumes and by occasional max out during peak periods. Exhibit 6-9 provides some typical ranges for maximum green based on various facility types. Maximum green values shown in Exhibit 6-9 should be used as a starting Exhibit 6-8 Maximum Green

Signal Timing Manual, Second Edion 6-10 Chapter 6. Intersecon/Uncoordinated Timing point and adjusted based on ield conditions. Good practice is to vary maximum green duration by time of day because trafic volumes could luctuate quite signiicantly between peak and off-peak hours. (Time-of-day plans are explained in detail in Section 6.3.) Phase Type Facility Type Maximum Green (Seconds) Through Major Arterial (> 40 mph) 50 to 70 Major Arterial (≤ 40 mph) 40 to 60 Minor Arterial 30 to 50 Collector, Local, or Driveway 20 to 40 Leˆ Turn Any 15 to 30 6.1.5 Passage Time (Unit Extension or Gap Time) Passage time (also called unit extension or gap time) is a parameter that can be used to terminate the current phase when a gap in trafic is identified. A gap indicates that trafic is no longer operating at eficient low rates and is often associated with headways greater than 2 to 3 seconds in each lane. Vehicle calls will extend green time on the current phase until a gap in detector occupancy is greater than the assigned passage time. If volumes are low enough, passage time allows a phase to end prior to its maximum green time. If the passage time is too short, the green may end prematurely— before vehicles have been adequately served. If the passage interval is set too long, there will be delays to other movements caused by unnecessary extension of the phase. Passage time essentially operates through a timer that starts to time down from the instant detector actuation is removed (i.e., a user leaves the detector). In a modern controller, the passage timer is constantly running and expires when it times out. A subsequent actuation (i.e., another user crossing the detector) will reset the passage timer if it has not yet expired. The green interval can be extended up to the maximum green time while the passage timer is still timing. The current phase will only gap out (i.e., terminate before the maximum green time) if all of the following conditions are met: 1. The minimum green timer has expired. 2. A call is waiting for service on a conlicting phase. 3. The passage timer has expired. Exhibit 6-10 illustrates vehicles moving over a typical setback detector and shows how that affects the passage timer and the eventual termination of the phase through a gap out. The mode of the detector (pulse or presence) is extremely important for passage time. Pulse mode provides a single pulse (only resetting after a vehicle leaves the detector), so the passage timer can time out with a car sitting over the detector. For this reason, pulse mode is not typically used in trafic signal control, except when system detectors are placed only to count vehicles (where queuing does not take place). If system detectors are used to measure occupancy, they must be in presence mode and should be located beyond normal intersection queues. Exhibit 6-9 Typical Values for Maximum Green Based on Facility Type “Headway” refers to the me between two successive vehicles as they pass a point on the roadway, measured from a common vehicle feature (e.g., front axle or front bumper). When the passage mer expires (mes out), it is commonly referred to as a “gap out.”

Signal Timing Manual, Second Edion 6-10 Chapter 6. Intersecon/Uncoordinated Timing point and adjusted based on ield conditions. Good practice is to vary maximum green duration by time of day because trafic volumes could luctuate quite signiicantly between peak and off-peak hours. (Time-of-day plans are explained in detail in Section 6.3.) Phase Type Facility Type Maximum Green (Seconds) Through Major Arterial (> 40 mph) 50 to 70 Major Arterial (≤ 40 mph) 40 to 60 Minor Arterial 30 to 50 Collector, Local, or Driveway 20 to 40 Leˆ Turn Any 15 to 30 6.1.5 Passage Time (Unit Extension or Gap Time) Passage time (also called unit extension or gap time) is a parameter that can be used to terminate the current phase when a gap in trafic is identified. A gap indicates that trafic is no longer operating at eficient low rates and is often associated with headways greater than 2 to 3 seconds in each lane. Vehicle calls will extend green time on the current phase until a gap in detector occupancy is greater than the assigned passage time. If volumes are low enough, passage time allows a phase to end prior to its maximum green time. If the passage time is too short, the green may end prematurely— before vehicles have been adequately served. If the passage interval is set too long, there will be delays to other movements caused by unnecessary extension of the phase. Passage time essentially operates through a timer that starts to time down from the instant detector actuation is removed (i.e., a user leaves the detector). In a modern controller, the passage timer is constantly running and expires when it times out. A subsequent actuation (i.e., another user crossing the detector) will reset the passage timer if it has not yet expired. The green interval can be extended up to the maximum green time while the passage timer is still timing. The current phase will only gap out (i.e., terminate before the maximum green time) if all of the following conditions are met: 1. The minimum green timer has expired. 2. A call is waiting for service on a conlicting phase. 3. The passage timer has expired. Exhibit 6-10 illustrates vehicles moving over a typical setback detector and shows how that affects the passage timer and the eventual termination of the phase through a gap out. The mode of the detector (pulse or presence) is extremely important for passage time. Pulse mode provides a single pulse (only resetting after a vehicle leaves the detector), so the passage timer can time out with a car sitting over the detector. For this reason, pulse mode is not typically used in trafic signal control, except when system detectors are placed only to count vehicles (where queuing does not take place). If system detectors are used to measure occupancy, they must be in presence mode and should be located beyond normal intersection queues. Exhibit 6-9 Typical Values for Maximum Green Based on Facility Type “Headway” refers to the me between two successive vehicles as they pass a point on the roadway, measured from a common vehicle feature (e.g., front axle or front bumper). When the passage mer expires (mes out), it is commonly referred to as a “gap out.” Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-11 When using presence mode, the speed of the vehicles crossing the detectors and the size of the detectors are important considerations for determining passage time. Large area detection (60 to 80 feet) allows passage times to be reduced to near zero, providing more eficient stop bar detection without fear of gap out, as even slow-moving vehicles typically do not leave a 60-foot gap. When stop bar detectors have passage time, there is effective “lost time” when the last vehicle departs the detection zone, as the signal does not turn yellow until after the vehicle has left the stop bar. In a typical dual-ring phasing sequence with leading left-turn phases, both passage timers for the two concurrent phases (typically two through phases) preceding the barrier need to time out before phase termination (by gap out) can occur. If the “simultaneous gap out” feature is used, an expired passage timer (that has reached zero) can be reset with subsequent actuation prior to phase termination if the phase in the Exhibit 6-10 Passage Time

Signal Timing Manual, Second Edion 6-12 Chapter 6. Intersecon/Uncoordinated Timing other ring has not gapped out. However, simultaneous gap out is not recommended in medium- to high-volume environments because it does not provide eficient operations. Note that an expired passage timer can be reset before the end of the minimum green interval regardless of the simultaneous gap out setting. The relationship between passage time and low rate is illustrated in Exhibit 6-11. Initially, low rate increases at the beginning of green to a maximum rate (following start-up lost time). In this example, the maximum low rate is shown at 1900 vehicles per hour. This example is meant to show how a change in passage time will change the point at which the phase ends. For example, a passage time of 2 seconds translates into a low rate of approximately 1800 vehicles per hour. Given a passage time of 2 seconds, the passage timer will not expire until 2 seconds after the low rate drops below 1800 vehicles per hour. So if this drop in low rate (below 1800 vehicles per hour) occurs at 15 seconds after the beginning of green, the trafic signal will turn yellow at 17 seconds. If the passage time is 3 seconds, then the passage timer will expire at 17 seconds with this low rate proile, and the trafic signal will turn yellow at 20 seconds. Note that the low rate values are for example purposes; intersections will have different low rate proiles. While the low rates associated with each passage time will remain constant, the point at which the low rate drops below those constant values will depend on local conditions. Exhibit 6-11 Passage Time and Flow Rate Relaonship

Signal Timing Manual, Second Edion 6-12 Chapter 6. Intersecon/Uncoordinated Timing other ring has not gapped out. However, simultaneous gap out is not recommended in medium- to high-volume environments because it does not provide eficient operations. Note that an expired passage timer can be reset before the end of the minimum green interval regardless of the simultaneous gap out setting. The relationship between passage time and low rate is illustrated in Exhibit 6-11. Initially, low rate increases at the beginning of green to a maximum rate (following start-up lost time). In this example, the maximum low rate is shown at 1900 vehicles per hour. This example is meant to show how a change in passage time will change the point at which the phase ends. For example, a passage time of 2 seconds translates into a low rate of approximately 1800 vehicles per hour. Given a passage time of 2 seconds, the passage timer will not expire until 2 seconds after the low rate drops below 1800 vehicles per hour. So if this drop in low rate (below 1800 vehicles per hour) occurs at 15 seconds after the beginning of green, the trafic signal will turn yellow at 17 seconds. If the passage time is 3 seconds, then the passage timer will expire at 17 seconds with this low rate proile, and the trafic signal will turn yellow at 20 seconds. Note that the low rate values are for example purposes; intersections will have different low rate proiles. While the low rates associated with each passage time will remain constant, the point at which the low rate drops below those constant values will depend on local conditions. Exhibit 6-11 Passage Time and Flow Rate Relaonship Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-13 The critical point to understand is that the passage timer is directly related to ef iciency at a signalized intersection. The challenge is getting as close to an optimum value of passage time as practical without short-timing a phase. (See Section 6.1.5.2 for information on the gap reduction feature.) If traf ic is light, giving a few extra seconds to less than ef icient operations (i.e., lows below the maximum rate) may have minimal impact on other traf ic. However, if the intersection is congested on any approach, a few extra seconds of inef icient low may be detrimental to other movements. As the passage time increases, the amount of inef icient low increases because the traf ic signal will remain green for the length of selected passage time after the last vehicle is detected at the associated low rate. Even if there are no vehicles after the last vehicle is detected at the measured low rate, the traf ic signal will remain green for the amount of passage time. 6.1.5.1 Operang Environment Consideraons for Passage Time Pedestrian actuations do not affect the passage time; pedestrian intervals will time regardless of whether the passage timer is timing or has expired. Bicycles are typically accommodated through an appropriate minimum green interval (see Exhibit 6-7) and are also not a factor when determining passage time. Under certain truck operating environment characteristics, increasing passage time to better accommodate trucks may be desirable depending on detection design. Considerations for trucks and transit can also be addressed with preferential treatment (discussed in Chapter 10). 6.1.5.2 Typical Values for Passage Time The appropriate passage time used for a particular signal phase depends on many factors, including detection design (e.g., type and number of detection zones per lane, as well as location and size of detection zones), detection mode (presence recommended), and approach speed. Ideally, detection is designed and passage time selected to ensure that the system provides ef icient queue service and safe phase termination on higher speed approaches. It is important to understand that the passage timer associated with a phase is based on a single detector in a single lane. Exhibit 6-12 provides typical passage time values to sustain a low rate of 1200 vehicles per hour (3-second headways) for a range of speeds and detection zone lengths. These values assume a single detector in a single lane (i.e., either a setback detector or a stop bar detector). Stop bar detectors are typically large area (e.g., 6 feet by 60 feet), and setback detectors are typically small area (e.g., 6 feet by 6 feet). If both setback detection and stop bar detection are available, the values in the table assume that the passage timer has been transferred exclusively to the setback detector. “Stop bar detector disconnect” is a feature in most modern controllers (and has a variety of different names). Setback detectors typically have passage times between 2 and 3 seconds if a single detector is used in each lane. If multiple lanes are associated with a phase and the detector inputs are wired separately, passage time can be timed on the detector function of modern controllers. There are generally two locations within modern controllers where passage time can be assigned—the detector function and the phase table. Note that if passage time is placed on the detector function, the passage time in the phase table should be zero so as not to have two or more timers interacting. The practitioner should reference speci ic controller manuals for detailed information.

Signal Timing Manual, Second Edion 6-14 Chapter 6. Intersecon/Uncoordinated Timing Detecon Zone Length (Feet) Passage Time (with a Headway of 3 Seconds) (Seconds) Posted Speed (MPH) 25 30 35 40 45 50 55 6 2.3 2.4 2.5 2.6 2.6 2.6 2.7 20 1.9 2.1 2.2 2.3 2.4 2.5 2.5 40 1.4 1.6 1.8 2.0 2.1 2.2 2.3 60 0.8 1.2 1.4 1.6 1.8 1.9 2.0 80 0.3 0.7 1.1 1.3 1.5 1.6 1.8 As shown in Exhibit 6-12, the longer the detection zone, the sh orter the required passage time. Shorter detection zones increase the probability that a phase will gap out due to sluggish trafic. Slow-moving vehicles (such as trucks) may need a longer passage time in order to reach a short detection zone, reset the passage timer, and continue through the intersection before the phase times out. Zones that are 60 feet or longer will have virtually no probability of gapping out even with little or no passage time. Using longer detection zones and shorter passage times results in minimal “lost time” once the last vehicle departs the stop bar. Values provided in Exhibit 6-12 can be used as a starting point, and if adjustments are desired, the following guiding principles should be followed (10): 1. Ensure queue clearance. The passage time should not be so small that the resulting headway causes the phase to have frequent premature gap outs unintentionally (i.e., a gap out that occurs before the queue is fully served). A premature gap out will leave a portion of the stopped queue unserved and, thereby, lead to increased delays and possible queue spillback. 2. Reduce max out frequency. The passage time should not be so large that the resulting operation causes the phase to have frequent max outs. A long passage time would allow even light trafic volumes to extend the green to max out. Users who are waiting in higher volume, conlicting phases may be delayed. In certain high-volume environments, gap reduction features may be used for more eficient gap outs, especially on multi-lane approaches. With a gap reduction feature, a higher passage time is used initially to prevent premature gap outs when vehicles are slowly clearing the intersection. After a speciied time (“time before reduction”), the passage time is reduced to a minimum gap value using a gradual reduction over a speciied time (“time to reduce”) as vehicular low decreases (shown in Exhibit 6-13). The time before reduction parameter establishes the time that is allowed to elapse after the arrival of a conlicting call and before the passage time begins to reduce. Once the time before reduction period expires, the passage time is reduced in a linear manner until the time to reduce period expires. Reducing the passage time to a minimum gap value allows the phase to gap out more easily as the phase progresses. Exhibit 6-12 Typical Values for Passage Time

Signal Timing Manual, Second Edion 6-14 Chapter 6. Intersecon/Uncoordinated Timing Detecon Zone Length (Feet) Passage Time (with a Headway of 3 Seconds) (Seconds) Posted Speed (MPH) 25 30 35 40 45 50 55 6 2.3 2.4 2.5 2.6 2.6 2.6 2.7 20 1.9 2.1 2.2 2.3 2.4 2.5 2.5 40 1.4 1.6 1.8 2.0 2.1 2.2 2.3 60 0.8 1.2 1.4 1.6 1.8 1.9 2.0 80 0.3 0.7 1.1 1.3 1.5 1.6 1.8 As shown in Exhibit 6-12, the longer the detection zone, the sh orter the required passage time. Shorter detection zones increase the probability that a phase will gap out due to sluggish trafic. Slow-moving vehicles (such as trucks) may need a longer passage time in order to reach a short detection zone, reset the passage timer, and continue through the intersection before the phase times out. Zones that are 60 feet or longer will have virtually no probability of gapping out even with little or no passage time. Using longer detection zones and shorter passage times results in minimal “lost time” once the last vehicle departs the stop bar. Values provided in Exhibit 6-12 can be used as a starting point, and if adjustments are desired, the following guiding principles should be followed (10): 1. Ensure queue clearance. The passage time should not be so small that the resulting headway causes the phase to have frequent premature gap outs unintentionally (i.e., a gap out that occurs before the queue is fully served). A premature gap out will leave a portion of the stopped queue unserved and, thereby, lead to increased delays and possible queue spillback. 2. Reduce max out frequency. The passage time should not be so large that the resulting operation causes the phase to have frequent max outs. A long passage time would allow even light trafic volumes to extend the green to max out. Users who are waiting in higher volume, conlicting phases may be delayed. In certain high-volume environments, gap reduction features may be used for more eficient gap outs, especially on multi-lane approaches. With a gap reduction feature, a higher passage time is used initially to prevent premature gap outs when vehicles are slowly clearing the intersection. After a speciied time (“time before reduction”), the passage time is reduced to a minimum gap value using a gradual reduction over a speciied time (“time to reduce”) as vehicular low decreases (shown in Exhibit 6-13). The time before reduction parameter establishes the time that is allowed to elapse after the arrival of a conlicting call and before the passage time begins to reduce. Once the time before reduction period expires, the passage time is reduced in a linear manner until the time to reduce period expires. Reducing the passage time to a minimum gap value allows the phase to gap out more easily as the phase progresses. Exhibit 6-12 Typical Values for Passage Time Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-15 The gap reduction features can also be demonstrated using the flow rate concept introduced in Exhibit 6-11. The point at which the phase ends will depend on the low rate proile, the gap reduction features, and conlicting traffic. Exhibit 6-14 illustrates how the use of a gap reduction feature (in this case, using a 3-second passage time and a 2-second minimum gap time) results in a phase termination between what could have been achieved with either a 2-second or 3-second passage time value. Exhibit 6-13 Relaonship between Passage Time, Minimum Gap, Time before Reducon, and Time to Reduce

6-16 Chapter 6. Intersecon/Uncoordinated Timing 6.1.6 Pedestrian Intervals The pedestrian phase consists of three intervals: walk, lashing don’t walk (FDW), and steady don’t walk (as shown in Exhibit 6-15). The walk interval typically begins at the start of the concurrent vehicular green interval and is used so that pedestrians can react to the start of the phase and move into the crosswalk. The FDW interval follows the walk interval and informs pedestrians that the phase is ending. Typically the FDW ends at the beginning of yellow, which is necessary for countdown pedestrian signals. (Note that ending the FDW at the beginning of yellow automatically satis ies the 3- second buffer interval required by the MUTCD [2].) While the FDW interval may be called the pedestrian clearance interval in some controllers, this is not necessarily accurate. The pedestrian clearance interval is the time required to cross the street, and the FDW interval is typically the pedestrian clearance interval reduced by the yellow change and red clearance intervals. While some agencies may choose longer pedestrian clearance times that do not include yellow and red clearance, it is not required. The steady don’t walk interval follows the FDW interval. The steady don’t walk time is not a programmable parameter in the controller. The duration of the steady don’t walk interval is simply the length of the phase minus the walk and FDW intervals. However, per the MUTCD, it must be displayed for at least 3 seconds before the release of any con licting vehicular movements (2). The pedestrian walk and FDW intervals typically time concurrently with vehicle intervals. The minimum duration of the walk is programmed in the controller; the actual walk interval may be longer depending on many other controller settings, which are discussed in Chapter 7. The practitioner must consider the in luence of the pedestrian Exhibit 6-14 Gap Reducon Features and Flow Rate Relaonship Signal Timing Manual, Second Edion

Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-17 intervals on the other users at the intersection. If the pedestrian intervals require more time than required for vehicles or permitted by the maximum green timer, the vehicle phase will continue to time until the pedestrian FDW interval finishes timing. 6.1.6.1 Operang Environment Consideraons for Pedestrian Intervals The length of pedestrian intervals may be increased based on pedestrian volumes, pedestrian characteristics (e.g., elderly pedestrians or school children) and facility characteristics (e.g., location of pedestrian push buttons and pedestrian crossing distances). A longer walk interval may be considered with high pedestrian volumes, and a longer FDW interval may be used near locations with users requiring extra time. Leading pedestrian intervals may be considered with high pedestrian volumes or with certain pedestrian safety issues (such as high volumes of turning vehicles). Leading pedestrian intervals are a treatment that allows pedestrians to establish their presence in a crosswalk, which reduces interference from turning vehicles. More information is provided in Section 6.1.6.6. 6.1.6.2 Typical Values for Pedestrian Walk Interval The walk interval should provide pedestrians with adequate time to perceive the walk indication and depart the curb before the FDW interval begins. In other words, it should be long enough to allow a pedestrian or multiple pedestrians at high-pedestrian- volume locations to enter the crosswalk. MUTCD (2) guidance states that the walk interval should be at least 7 seconds in length. In areas with high pedestrian volumes (such as school zones, central business districts (CBDs), and sports and event venues), longer walk intervals should be considered. Typical values for the pedestrian walk interval are provided in Exhibit 6-16. These values are based on information from the MUTCD and Trafic Control Devices Handbook (2, 5). Exhibit 6-15 Pedestrian Intervals The length of the walk interval may be established in local agency policy.

Signal Timing Manual, Second Edion 6-18 Chapter 6. Intersecon/Uncoordinated Timing Condions Walk Interval (Seconds) High-pedestrian-volume area (e.g., school, CBD, or sports and event venue) 10 to 15 Typical pedestrian volume and longer cycle length 7 to 10 Typical pedestrian volume and shorter cycle length 7 Negligible pedestrian volume and otherwise long cycle length 4 6.1.6.3 Typical Values for Pedestrian Clearance Pedestrian clearance is the time required for a pedestrian to complete crossing the street, assuming the walk interval has expired and the FDW interval has just begun. One special-use option is using pedestrian detection to automatically adjust the pedestrian clearance time based on actual pedestrian walking speeds or clearance of the crosswalk, but the more traditional process is to calculate the required pedestrian clearance using a predetermined walking speed. The MUTCD (2) states that pedestrian clearance times should be suf‚icient to allow a pedestrian walking at a speed of 3.5 feet per second to cross from the curb or shoulder to at least (a) the far side of the traveled way or (b) to a median of suf‚icient width for pedestrians to wait (2). Where slower pedestrians routinely use a crossing, a walking speed less than 3.5 feet per second may be considered when determining the pedestrian clearance time. Alternatively, the MUTCD (2) outlines an option to use a walking speed of up to 4 feet per second to evaluate whether the pedestrian clearance time is suf‚icient. This option may be applied at locations where an extended push button press function has been installed to provide slower pedestrians an opportunity to request and receive a longer pedestrian clearance time. An example of the extended push button treatment signage is shown in Exhibit 6-17. Using an established walking speed, pedestrian clearance time can be calculated using Equation 6-5. To calculate the FDW time that is routinely programmed in the signal controller phase table, the practitioner should subtract the yellow change and red clearance interval times from the calculated pedestrian clearance time. where PCT = pedestrian clearance time (seconds), Dc = pedestrian crossing distance (feet), and vp = pedestrian walking speed (feet per second). Typical values for pedestrian clearance time (calculated using Equation 6-5), assuming a walking speed of 3.5 feet per second, for various pedestrian crossing distances are shown in Exhibit 6-18. Exhibit 6-16 Typical Values for Pedestrian Walk Interval Exhibit 6-17 Example of Extended Push BuŒon Press Funcon Signage Equaon 6-5

Signal Timing Manual, Second Edion 6-18 Chapter 6. Intersecon/Uncoordinated Timing Condions Walk Interval (Seconds) High-pedestrian-volume area (e.g., school, CBD, or sports and event venue) 10 to 15 Typical pedestrian volume and longer cycle length 7 to 10 Typical pedestrian volume and shorter cycle length 7 Negligible pedestrian volume and otherwise long cycle length 4 6.1.6.3 Typical Values for Pedestrian Clearance Pedestrian clearance is the time required for a pedestrian to complete crossing the street, assuming the walk interval has expired and the FDW interval has just begun. One special-use option is using pedestrian detection to automatically adjust the pedestrian clearance time based on actual pedestrian walking speeds or clearance of the crosswalk, but the more traditional process is to calculate the required pedestrian clearance using a predetermined walking speed. The MUTCD (2) states that pedestrian clearance times should be suf‚icient to allow a pedestrian walking at a speed of 3.5 feet per second to cross from the curb or shoulder to at least (a) the far side of the traveled way or (b) to a median of suf‚icient width for pedestrians to wait (2). Where slower pedestrians routinely use a crossing, a walking speed less than 3.5 feet per second may be considered when determining the pedestrian clearance time. Alternatively, the MUTCD (2) outlines an option to use a walking speed of up to 4 feet per second to evaluate whether the pedestrian clearance time is suf‚icient. This option may be applied at locations where an extended push button press function has been installed to provide slower pedestrians an opportunity to request and receive a longer pedestrian clearance time. An example of the extended push button treatment signage is shown in Exhibit 6-17. Using an established walking speed, pedestrian clearance time can be calculated using Equation 6-5. To calculate the FDW time that is routinely programmed in the signal controller phase table, the practitioner should subtract the yellow change and red clearance interval times from the calculated pedestrian clearance time. where PCT = pedestrian clearance time (seconds), Dc = pedestrian crossing distance (feet), and vp = pedestrian walking speed (feet per second). Typical values for pedestrian clearance time (calculated using Equation 6-5), assuming a walking speed of 3.5 feet per second, for various pedestrian crossing distances are shown in Exhibit 6-18. Exhibit 6-16 Typical Values for Pedestrian Walk Interval Exhibit 6-17 Example of Extended Push BuŒon Press Funcon Signage Equaon 6-5 Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-19 Pedestrian Crossing Distance (Feet) Calculated Pedestrian Clearance Time (Seconds) 40 11 60 17 80 23 100 29 6.1.6.4 Typical Values for Pedestrian Flashing Don’t Walk Interval The pedestrian FDW interval (incorrectly called pedestrian clearance in some controller phase tables) can be determined by reducing the calculated intersection pedestrian clearance time by the yellow change and red clearance times. The FDW time displayed during the yellow change and red clearance intervals is essentially the “buffer” time before a conlicting movement. Some agencies may prefer a more conservative approach, and will not reduce the calculated pedestrian clearance time by the yellow change and red clearance times. A practitioner should verify standard practice through a review of jurisdiction policies. 6.1.6.5 Addional Guidance on Pedestrian Intervals—4-Second Walk While pedestrian walk intervals of 7 seconds are usually appropriate in most situations, walk intervals as short as 4 seconds may be used (2) if pedestrian volumes and characteristics do not necessitate the full 7-second walk interval. MUTCD (2) guidance states that the total of the 4-second walk and pedestrian clearance (calculated at 3.5 feet per second) should be enough time for a pedestrian to travel from the pedestrian detector (or if no detector is present, a location 6 feet from the edge of curb or pavement) at the beginning of the walk signal indication to the far side of the traveled way or the median, while traveling in the crosswalk at a walking speed of 3 feet per second (see Exhibit 6-19). Any additional time that is required to satisfy the condition of the 3-feet-per-second guidance should be added to the walk interval (2). Exhibit 6-18 Calculated Values for Pedestrian Clearance Time (Based on a Walking Speed of 3.5 Feet per Second) Exhibit 6-19 Pedestrian Interval Requirements Based on Walking Speed

6-20 Chapter 6. Intersecon/Uncoordinated Timing 6.1.6.6 Addional Guidance on Pedestrian Intervals—Leading Pedestrian Interval A leading pedestrian interval allows the walk indication for a pedestrian phase to be displayed prior to the associated vehicle phase. This treatment allows a pedestrian to establish right-of-way in an intersection and can also aid in pedestrian visibility for drivers, bicyclists, and other system users. In the case of special pedestrian treatments, the MUTCD (2) states that if a leading pedestrian interval is used, it should be at least 3 seconds in duration, and consideration should be given to prohibiting turns across the crosswalk during this time. Exhibit 6-20 uses a ring-and-barrier diagram to illustrate a phasing sequence with leading pedestrian intervals on Phases 2 and 6. 6.1.7 Dual Entry The dual (double) entry parameter is used to call vehicle phases that can time concurrently, even if only one of the phases is receiving an active call. For example, if dual entry is active for Phases 4 and 8, and Phase 4 receives a call but no call is placed on Phase 8, Phase 8 will still be displayed along with Phase 4. The most common use of dual entry is to activate the parameter for compatible through movements. If the dual entry parameter is not selected, a vehicle call on a phase will only result in the timing of that phase in the absence of a call on the compatible phase. 6.1.8 Recalls and Memory Modes The recall parameter causes the controller to place a call automatically for a speciˆied phase regardless of the presence of any detector-actuated calls. There are four types of recalls: minimum recall (also known as vehicle recall), maximum recall, soft recall, and pedestrian recall. If no recalls or serviceable calls exist, the controller may be conˆigured to rest in red or the last green. Descriptions are the following: • Minimum Recall: The minimum recall parameter causes the controller to place a call for vehicle service on a phase in order to serve at least its minimum green duration. Exhibit 6-20 Leading Pedestrian Intervals Signal Timing Manual, Second Edion

Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-21 • Maximum Recall: The maximum recall parameter causes the controller to place a continuous call for vehicle service on a phase in order to run its maximum green duration every cycle. • Soft Recall: The soft recall parameter causes the controller to place a call for vehicle service on a phase in the absence of a serviceable conlicting call. • Pedestrian Recall: The pedestrian recall parameter causes the controller to place a continuous call for pedestrian service on a phase, resulting in the controller timing its walk and FDW intervals every cycle. • Red Rest: All phases may rest in red state when no serviceable calls exist in the ring and none of the above recall modes are used. • Green Rest: If there is no serviceable call and no recall or red rest, the controller will rest in the last green. Memory modes refer to the controller’s ability to “remember” (i.e., retain) a detector actuation for a particular phase when an actuation is received during the red interval (and optionally, the yellow interval). One of two modes can be used—non-locking or locking. Memory mode is typically set on a per-phase basis, although some trafic signal controllers may have memory mode settings available for each detector channel input. The non-locking mode is typically the default mode, but regardless of the chosen detector mode, all actuations received during the green interval are treated as non- locking by the controller. Descriptions of the modes are the following: • Non-Locking Mode: In the non-locking mode, an actuation received from a detector is not retained by the controller after the actuation is dropped by the detection unit. The controller recognizes the actuation only during the time that it is held present by the detection unit. • Locking Mode: In the locking mode, the irst actuation received by the controller on a speciied channel during the red interval (and optionally, yellow interval) is used by the controller to trigger a continuous call for service. This call is retained until the assigned phase is served, regardless of whether any vehicles are waiting to be served. 6.1.8.1 Operang Environment Consideraons for Recalls and Memory Modes The practitioner should determine the recall setting (or allow red rest) based on the operating environment. For example, arterials are likely best served by soft recall if detection exists on all phases. Pedestrian recall, on the other hand, may be used at locations and/or times with high pedestrian volumes. 6.1.8.2 Typical Sengs for Recalls and Memory Modes Certain recall and memory mode settings may be more appropriate than others depending on the detection design and intended signal operations. Exhibit 6-21 provides a summary of typical detection designs and considerations for various recall and memory mode settings. This guidance assumes a single detector per lane. Intersections with more complicated detector designs would have different settings and need to be evaluated on a case-by-case basis. Recall and memory modes are controller sengs that place calls on a parcular phase so that the phase will be served either automacally or based on past vehicle actuaons, respecvely.

Signal Timing Manual, Second Edion 6-22 Chapter 6. Intersecon/Uncoordinated Timing Se ngs Typical Detecon Designs Reasons for Use Re ca lls No Recalls Stop bar detectors or setback detectors with locking mode Relavely light traffic demand, and phases need not be served every cycle. Minimum Recall (Vehicle Recall) Setback detectors with non- locking mode Phases are expected to be served every cycle (e.g., on major street through movements) with green me to be extended based on vehicle actuaons. Maximum Recall No detectors Fixed-me operaon is desired, or gapping out is not desired. Maximum recall is typically not used at fully-actuated intersecons with good detecon systems and proper passage me seˆngs. So‰ Recall Setback detectors with locking mode Use on major street through movements to ensure these movements will dwell in green in the absence of calls on conflicng phases and allow major street through movements to be skipped in the absence of major street phase calls when calls exist on other phases. Pedestrian Recall No pedestrian detectors Pedestrian demand is expected to be high, and pedestrian phases are expected to be served every cycle. Red Rest Stop bar detectors or setback detectors with locking mode Typically at intersecons with no definable major or minor streets. M em or y M od es Non-Locking Mode Stop bar detectors Allows permied movements (e.g., right- turn-on-red) to be completed without invoking a phase change. Locking Mode Setback detectors with no stop bar detectors Use on major street through movements associated with a low percentage of turning vehicles when recalls are not used. Assuming Phases 2 and 6 are assigned to the major street through movements, Exhibit 6-22 shows the typical settings on recalls and memory modes at a fully-actuated intersection. At fully-actuated intersections where there are not deinable major or minor streets, some agencies may prefer to dwell in the last phase, dwell in the next through phase, or dwell in red. This allows the intersection to dwell in the most appropriate state in the absence of any vehicle or pedestrian calls. Sengs On for Phases Off for Phases Re ca lls Minimum Recall (Vehicle Recall) None All Phases Maximum Recall None All Phases So… Recall 2 and 6 All Phases (Except 2 and 6) Pedestrian Recall None All Phases M em or y M od es Locking Mode1 None All Phases 1 Common names in traffic signal controllers include “Memory,” “Red Lock,” etc. “Yellow Lock” provides similar operations, but also allows actuations received during the yellow interval to be retained. Exhibit 6-21 Recall and Memory Mode Consideraons Exhibit 6-22 Typical Se‹ngs on Recalls and Memory Modes at a Fully-Actuated Intersecon

Signal Timing Manual, Second Edion 6-22 Chapter 6. Intersecon/Uncoordinated Timing Se ngs Typical Detecon Designs Reasons for Use Re ca lls No Recalls Stop bar detectors or setback detectors with locking mode Relavely light traffic demand, and phases need not be served every cycle. Minimum Recall (Vehicle Recall) Setback detectors with non- locking mode Phases are expected to be served every cycle (e.g., on major street through movements) with green me to be extended based on vehicle actuaons. Maximum Recall No detectors Fixed-me operaon is desired, or gapping out is not desired. Maximum recall is typically not used at fully-actuated intersecons with good detecon systems and proper passage me seˆngs. So‰ Recall Setback detectors with locking mode Use on major street through movements to ensure these movements will dwell in green in the absence of calls on conflicng phases and allow major street through movements to be skipped in the absence of major street phase calls when calls exist on other phases. Pedestrian Recall No pedestrian detectors Pedestrian demand is expected to be high, and pedestrian phases are expected to be served every cycle. Red Rest Stop bar detectors or setback detectors with locking mode Typically at intersecons with no definable major or minor streets. M em or y M od es Non-Locking Mode Stop bar detectors Allows permied movements (e.g., right- turn-on-red) to be completed without invoking a phase change. Locking Mode Setback detectors with no stop bar detectors Use on major street through movements associated with a low percentage of turning vehicles when recalls are not used. Assuming Phases 2 and 6 are assigned to the major street through movements, Exhibit 6-22 shows the typical settings on recalls and memory modes at a fully-actuated intersection. At fully-actuated intersections where there are not deinable major or minor streets, some agencies may prefer to dwell in the last phase, dwell in the next through phase, or dwell in red. This allows the intersection to dwell in the most appropriate state in the absence of any vehicle or pedestrian calls. Sengs On for Phases Off for Phases Re ca lls Minimum Recall (Vehicle Recall) None All Phases Maximum Recall None All Phases So… Recall 2 and 6 All Phases (Except 2 and 6) Pedestrian Recall None All Phases M em or y M od es Locking Mode1 None All Phases 1 Common names in traffic signal controllers include “Memory,” “Red Lock,” etc. “Yellow Lock” provides similar operations, but also allows actuations received during the yellow interval to be retained. Exhibit 6-21 Recall and Memory Mode Consideraons Exhibit 6-22 Typical Se‹ngs on Recalls and Memory Modes at a Fully-Actuated Intersecon Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-23 6.2 DETECTOR CONFIGURATIONS This section explains the following detector parameters commonly used at signalized intersections: • Delay, • Extend/carry-over/stretch time, and • Detector switching. These detector parameters are only applicable to vehicle detectors (not pedestrian detectors). 6.2.1 Delay Delay is used to temporarily disable detector output for a phase, essentially preventing vehicle actuations from being recognized right away by the signal controller. An actuation is not made available unless the delay timer has expired and the detection zone is still occupied. Delay can either be programmed on the detector or in the controller. However, the signal timing practitioner should be careful not to program delay into both the detector and controller, or calls may be delayed longer than desired. The delay timer is only active when its assigned phase is not green. Delay is commonly applied to (1) minor street stop bar detectors in exclusive right- turn lanes and (2) left-turn lane detectors. Delay is used to prevent erroneous calls from being registered in the controller (e.g., detectors in left-turn lanes may accidentally be traversed by vehicles on another phase or cut across by perpendicular left-turning vehicles) or to allow permitted movements to take place without calling a protected phase. Exhibit 6-23 illustrates delay assigned to stop bar detectors in an exclusive right- turn lane. 6.2.1.1 Typical Values for Delay Appropriate values for delay depend on how long a vehicle is expected to occupy a detector before the vehicle leaves that detector. Exhibit 6-24 provides a summary of typical values for the following common applications: • Delay may be used with stop bar, presence mode detection for turn movements from exclusive lanes. For right-turn-lane detection, delay should be considered when the capacity for right-turn-on-red exceeds the right- turn volume or a con…licting movement is on recall. If right-turn-on-red capacity is limited, then delay may only serve to degrade intersection ef…iciency by further delaying right-turning vehicles. The delay setting could range from 8 to 12 seconds, with the larger values used for higher cross- street volumes (10). • Delay may also be used to prevent an erroneous call from being registered in the controller if vehicles tend to traverse over another phase’s detection zone. For example, left-turning vehicles often cut across the perpendicular left-turn lane at the end of their turning movement. A detector delay coupled with non-locking memory would prevent a call from being placed for the unoccupied detector. The delay value depends on how long a detector is erroneously occupied. Typically, values range from 2 to 5 seconds.

Signal Timing Manual, Second Edion 6-24 Chapter 6. Intersecon/Uncoordinated Timing Exhibit 6-23 Delay Timer

Signal Timing Manual, Second Edion 6-24 Chapter 6. Intersecon/Uncoordinated Timing Exhibit 6-23 Delay Timer Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-25 Common Applicaons for Delay Applicable Detectors Delay (Seconds) Right-Turn-on-Red in Right-Turn Lanes Minor street stop bar detectors in exclusive right-turn lanes 8 to 12 Erroneous Call Prevenon for Le€- Turn Lanes Stop bar detectors in le€-turn lanes 2 to 5 6.2.2 Extend Time (Carry-Over or Stretch Time) Extend time (also called carry-over or stretch time) is a method used to increase the duration of an actuation on a detector. Much like delay, extend time can be programmed on the detector or in the controller. Signal timing practitioners should make sure that extend time is not programmed both on the detector and in the controller, or calls may be extended longer than desired. The extend timer begins the instant the actuation channel input is inactive. Thus, an actuation that is 1 second in duration on the detector input can be extended to 3 seconds if the extend parameter is set to 2 seconds. This process is illustrated in Exhibit 6-25. The extend parameter is typically used with detection designs that combine multiple setback detectors on high-speed approaches. The objective when used on high- speed approaches (with multiple detectors per lane) is to extend the green interval, allowing just enough time for a vehicle approaching the intersection to reach the next downstream detector. The vehicle will then be able to place a new call for green extension if traveling at the assumed speed. This feature can also be used to provide lane-by-lane passage time. Instead of the passage time being controlled by the phase table, the detector times the extend parameter, allowing each lane to be timed separately. If stop bar detection is used, it should use the detector disconnect feature upon gap out. This allows the standing queue to discharge, but prevents the phase from being continually extended. 6.2.2.1 Typical Values for Extend Time with Mulple Detectors per Lane The extend time assigned to a detector is dependent on the approach speed, detector size, and the distance between the subject detector and the next downstream detector. In order to maintain ef„iciency, typical values range up to 2 seconds. More information about speci„ic extend time values can be found in the Manual of Trafic Detector Design (11). Exhibit 6-24 Typical Values for Delay

Signal Timing Manual, Second Edion 6-26 Chapter 6. Intersecon/Uncoordinated Timing Exhibit 6-25 Extend Timer

Signal Timing Manual, Second Edion 6-26 Chapter 6. Intersecon/Uncoordinated Timing Exhibit 6-25 Extend Timer Signal Timing Manual, Second Edion Chapter 6. Intersecon/Uncoordinated Timing 6-27 6.2.3 Detector Switching Detector switching is a common detector function in traf ic signal controllers that allows detectors to call and extend one phase (extend phase) and then send calls to another phase (switch phase) once the extend phase ends. Detector switching allows the programmed switch phase to be extended after the extend phase terminates. It is typically only effective when the switch phase is green. Also, detector switching does not typically switch phase calls. Detector switching is commonly used on left-turn lane detectors under protected- permitted operations. Vehicles detected in left-turn lanes are switched to extend the through phase during the permitted portion of the phase, in order to provide more time for vehicles making left-turn movements. Exhibit 6-26 provides a summary of typical detector switching settings at a standard eight-phase intersection with protected- permitted operations on all approaches. Phase Extend Phase Switch Phase (with Five- Secon Signal Head Protected- Permied Operaons) Switch Phase (with FYA Protected-Permied Operaons) 1 1 6 2 3 3 8 4 5 5 2 6 7 7 4 8 6.3 TIME-OF-DAY PLANS Most controllers allow signal timing parameter values to vary by time of day, week, or year. The schedule for these timing plan changes is referred to as the time-of-day plan. It provides information to the controller about which set of signal timing parameters should be used depending on the established schedule. Time-of-day plans should be developed for speci ic outcomes and can be used to help an agency meet its objectives during different time periods. Determining when traf ic conditions typically change can help a practitioner decide how many time-of-day plans are required. Most intersections experience a peak period during the morning and evening, so the morning and evening peaks may have different timing plans (with different signal timing values) than the rest of the day. For example, the maximum green on Phase 2 during a weekday may be programmed for 20 seconds most of the day and 30 seconds during the peak periods. In addition to timing plan changes throughout a day, separate plans may be warranted for weekdays, weekends, or even speci ic days (i.e., Friday on a holiday weekend) based on variation in travel patterns and volumes. For example, tourist areas that experience a large luctuation in traf ic low throughout the year may ind it bene icial to develop timing plans for the tourist and non-tourist seasons. The practitioner will need to verify which parameters can be changed by time of day in the controller, but should consider different values when selecting the signal timing parameters explained throughout this chapter. Exhibit 6-26 Typical Sengs for Detector Switching under Protected-Permi‚ed Operaons

Signal Timing Manual, Second Edion 6-28 Chapter 6. Intersecon/Uncoordinated Timing 6.4 REFERENCES 1. Uniform Vehicle Code, Millennium Edition. National Committee on Uniform Traf ic Laws and Ordinances, Alexandria, Virginia, 2000. 2. Manual on Uniform Traf ic Control Devices for Streets and Highways, 2009 Edition. United States Department of Transportation, Federal Highway Administration, Washington, D.C., 2009. 3. Determining Vehicle Signal Change and Clearance Intervals. Institute of Transportation Engineers, Washington, D.C., 1994. 4. Traf ic Engineering Handbook, 6th Edition. Institute of Transportation Engineers, Washington, D.C., 2009. 5. Traf ic Control Devices Handbook. Institute of Transportation Engineers, Washington, D.C., 2001. 6. McGee, Sr., H., K. Moriarty, K. Eccles, M. Liu, T. Gates, and R. Retting. NCHRP Report 731: Guidelines for Timing Yellow and All-Red Intervals at Signalized Intersections. Transportation Research Board of the National Academies, Washington, D.C., 2012. 7. Tarnoff, P. J. Traf ic Signal Clearance Intervals. In ITE Journal, Institute of Transportation Engineers, Washington, D.C., 2004, pp. 20–24. 8. Souleyrette, R. R., M. M. O’Brien, T. McDonald, H. Preston, and R. Storm. Effectiveness of All-Red Clearance Interval on Intersection Crashes. Report MN/RC-2004-26, Minnesota Department of Transportation, 2004. 9. California Manual on Uniform Traf ic Control Devices, 2012 Edition. California Department of Transportation, Sacramento, California, 2012. 10. Bonneson, J. A., and M. Abbas. Intersection Video Detection Manual. Report FHWA/TX-03/4285-2, Texas Department of Transportation, Austin, Texas, 2002. 11. Bonneson, J. A., and P. T. McCoy. Manual of Traf ic Detector Design, 2nd Edition. Institute of Transportation Engineers, Washington D.C., 2005.

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 812: Signal Timing Manual - Second Edition, covers fundamentals and advanced concepts related to signal timing. The report addresses ways to develop a signal timing program based on the operating environment, users, user priorities by movement, and local operational objectives.

Advanced concepts covered in the report include the systems engineering process, adaptive signal control, preferential vehicle treatments, and timing strategies for over-saturated conditions, special events, and inclement weather.

An overview PowerPoint presentation accompanies the report.

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