902.23 Traffic Signal Phasing and Operation - Revision history

RollerA: /* 902.23.11.3.2.1 Time Base Coordination (TBC) */

2025-11-25T18:53:33Z

902.23.11.3.2.1 Time Base Coordination (TBC)

← Older revision		Revision as of 13:53, 25 November 2025
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	At 6 a.m., this controller will look back to midnight and calculate when to time an offset break by starting the first 70-second cycle at midnight.		At 6 a.m., this controller will look back to midnight and calculate when to time an offset break by starting the first 70-second cycle at midnight.

	[[~~image~~:902.~~5.5~~.3~~.2.1.1~~.jpg\|center\|500px]]		[[File:Figure 902.23.3.jpg\|center\|500px]]

	Controller 2 - Sync Reference: Start of Timing Plan		Controller 2 - Sync Reference: Start of Timing Plan
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	At 6 a.m., this controller will begin to time offset breaks every 70 seconds.		At 6 a.m., this controller will begin to time offset breaks every 70 seconds.

	[[~~image~~:902.5.~~5.3.2.1.2~~.jpg\|center\|500px]]		[[File:Figure 902.23.4.jpg\|center\|500px]]

	Due to the use of two different references, Controller 1's offset break is 30 seconds after Controller 2's. Therefore, if different offset references are used the coordination between the signals will be lost.		Due to the use of two different references, Controller 1's offset break is 30 seconds after Controller 2's. Therefore, if different offset references are used the coordination between the signals will be lost.
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	Because a TBC system does not have a master controller to give each local a signal as to what timing plan to run, each local is responsible for changing timing plans. The timing plans can be designated by different numbers (i.e. Cycle 3/Split 1 or Timing Plan 06) if the cycle length is similar, but for consistency, it is advisable to keep the same designation in each controller for each timing plan.		Because a TBC system does not have a master controller to give each local a signal as to what timing plan to run, each local is responsible for changing timing plans. The timing plans can be designated by different numbers (i.e. Cycle 3/Split 1 or Timing Plan 06) if the cycle length is similar, but for consistency, it is advisable to keep the same designation in each controller for each timing plan.

	The start of each timing plan is typically at the same time for each controller, especially if the offset reference is the start of the timing plan. If all controllers are operating at a midnight reference for offset breaks, then timing plans which begin at slightly staggered times could be used with a slight delay in the onset of proper coordination. If the offset reference is at the start of the timing plan, then slightly staggered start times will give different times that the offset breaks start, and ruin coordination.		The start of each timing plan is typically at the same time for each controller, especially if the offset reference is the start of the timing plan. If all controllers are operating at a midnight reference for offset breaks, then timing plans which begin at slightly staggered times could be used with a slight delay in the onset of proper coordination. If the offset reference is at the start of the timing plan, then slightly staggered start times will give different times that the offset breaks start, and ruin coordination.

	=====902.23.11.3.2.2 Ethernet-Over-Copper Interconnect=====		=====902.23.11.3.2.2 Ethernet-Over-Copper Interconnect=====

RollerA: /* 902.23.11.2.5 Determine Offsets and Transition in Each Timing Plan */

2025-11-25T18:51:15Z

902.23.11.2.5 Determine Offsets and Transition in Each Timing Plan

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	'''Guidance.''' The most common way to represent the flow of traffic on an arterial is the use of a time-space diagram. This type of graphical representation uses an x-y axis plot of red and green time, phase sequences, cycle lengths, and intersection spacing to display how well a platoon of vehicles moves from one end of the arterial to the other. The x-axis is a scale of the intersections by feet, and the y-axis represents the time scale in seconds (the x- and y-axis might be switched depending on the program used to create it.). Multiple cycles are laid out on the y-axis, with solid lines representing mainline red time. A green band represents the flow of vehicles whose slope represents the speed of the platoon along the artery. An example is shown below.		'''Guidance.''' The most common way to represent the flow of traffic on an arterial is the use of a time-space diagram. This type of graphical representation uses an x-y axis plot of red and green time, phase sequences, cycle lengths, and intersection spacing to display how well a platoon of vehicles moves from one end of the arterial to the other. The x-axis is a scale of the intersections by feet, and the y-axis represents the time scale in seconds (the x- and y-axis might be switched depending on the program used to create it.). Multiple cycles are laid out on the y-axis, with solid lines representing mainline red time. A green band represents the flow of vehicles whose slope represents the speed of the platoon along the artery. An example is shown below.

	[[~~image~~:902.7.~~4.7~~.gif\|center\|600px]]		[[File:Figure 902.23.2.gif\|center\|600px]]


	It will be assumed the user has a computer with a time-space diagram program available. Hand-drawn time-space diagrams are cumbersome, difficult to lay out, and nearly impossible to modify when changes are needed on the street. All further discussion on time-space diagrams will be based on the computer applications.		It will be assumed the user has a computer with a time-space diagram program available. Hand-drawn time-space diagrams are cumbersome, difficult to lay out, and nearly impossible to modify when changes are needed on the street. All further discussion on time-space diagrams will be based on the computer applications.

RollerA: /* 902.23.8.8 Phase Re-Service */

2025-11-25T18:49:12Z

902.23.8.8 Phase Re-Service

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	Advantages to this setting are in reducing the delay for re-serviced left turns. Again, care is to be taken when using this setting at a coordinated intersection. Re-service will not be possible when used with coordinated phases, and available time to re-service side street phases will be almost non-existent. This setting works best at isolated intersections, or when coordinated signals are not running coordination (Free Operation).		Advantages to this setting are in reducing the delay for re-serviced left turns. Again, care is to be taken when using this setting at a coordinated intersection. Re-service will not be possible when used with coordinated phases, and available time to re-service side street phases will be almost non-existent. This setting works best at isolated intersections, or when coordinated signals are not running coordination (Free Operation).

	[[~~image~~:902.5.3.6.gif\|thumb\|400px\|center\|<center>'''Figure 902.23.8.8'''</center>]]		[[File:Figure 902.23.8.8.gif\|thumb\|400px\|center\|<center>'''Figure 902.23.8.8'''</center>]]

	=={{SpanID\|902.23.9}}902.23.9 Power Outages at Signalized Intersections==		=={{SpanID\|902.23.9}}902.23.9 Power Outages at Signalized Intersections==

RollerA: /* 902.23.8.3 Detection on High-Speed Approaches */

2025-11-25T18:48:13Z

902.23.8.3 Detection on High-Speed Approaches

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	Advanced detection can also be helpful to the motorist by enabling the signal to terminate a conflicting phase (when possible an appropriate) while the motorist is still approaching the intersection; thus providing the motorist a “quicker” green light upon arriving at the intersection.		Advanced detection can also be helpful to the motorist by enabling the signal to terminate a conflicting phase (when possible an appropriate) while the motorist is still approaching the intersection; thus providing the motorist a “quicker” green light upon arriving at the intersection.

	[[File:Figure 902.23.8.3.gif\|thumb\|550px\|center\|<Center>'''~~Fig.~~ 902.23.8.3'''</center>]]		[[File:Figure 902.23.8.3.gif\|thumb\|550px\|center\|<Center>'''Figure 902.23.8.3'''</center>]]

RollerA: /* 902.23.8.3 Detection on High-Speed Approaches */

2025-11-25T18:47:41Z

902.23.8.3 Detection on High-Speed Approaches

← Older revision		Revision as of 13:47, 25 November 2025
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	Advanced detection can also be helpful to the motorist by enabling the signal to terminate a conflicting phase (when possible an appropriate) while the motorist is still approaching the intersection; thus providing the motorist a “quicker” green light upon arriving at the intersection.		Advanced detection can also be helpful to the motorist by enabling the signal to terminate a conflicting phase (when possible an appropriate) while the motorist is still approaching the intersection; thus providing the motorist a “quicker” green light upon arriving at the intersection.

	[[~~image~~:902.5.~~3.4~~.3.gif\|thumb\|550px\|center\|<Center>'''Fig. 902.23.8.3'''</center>]]		[[File:Figure 902.23.8.3.gif\|thumb\|550px\|center\|<Center>'''Fig. 902.23.8.3'''</center>]]


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	\|align="center"\|'''90'''\|\|align="center"\|'''132.0'''\|\|align="center"\|132\|\|align="center"\|660\|\|align="center"\|1056\|\|align="center"\|1320\|\|align="center"\|1980\|\|align="center"\|2640\|\|align="center"\|3300\|\|align="center"\|3960\|\|align="center"\|4620\|\|align="center"\|5280\|\|align="center"\|5940\|\|align="center"\|6600\|\|align="center"\|7260\|\|align="center"\|7920		\|align="center"\|'''90'''\|\|align="center"\|'''132.0'''\|\|align="center"\|132\|\|align="center"\|660\|\|align="center"\|1056\|\|align="center"\|1320\|\|align="center"\|1980\|\|align="center"\|2640\|\|align="center"\|3300\|\|align="center"\|3960\|\|align="center"\|4620\|\|align="center"\|5280\|\|align="center"\|5940\|\|align="center"\|6600\|\|align="center"\|7260\|\|align="center"\|7920
	\|}		\|}


	===902.23.8.4 Delay and Extend Detector Settings===		===902.23.8.4 Delay and Extend Detector Settings===

RollerA: /* 902.23.8.2 Advance Detectors and Gap Reduction */

2025-11-25T18:45:57Z

902.23.8.2 Advance Detectors and Gap Reduction

← Older revision		Revision as of 13:45, 25 November 2025
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	'''Support.''' Advance detectors are used for through movements on the major roadway to create a detection zone in advance of the stop bar, especially if the 85<sup>th</sup> percentile speeds on the major roadway are 45 mph or more. These detectors are typically placed a distance of five seconds behind the stop bar at the 85<sup>th</sup> percentile speed. Because of the long spacing from the stop bar, sole use of the standard passage time would result in extended green times with large gaps. Gap reduction control provides a means of decreasing the passage time as the speed of the flow increases.		'''Support.''' Advance detectors are used for through movements on the major roadway to create a detection zone in advance of the stop bar, especially if the 85<sup>th</sup> percentile speeds on the major roadway are 45 mph or more. These detectors are typically placed a distance of five seconds behind the stop bar at the 85<sup>th</sup> percentile speed. Because of the long spacing from the stop bar, sole use of the standard passage time would result in extended green times with large gaps. Gap reduction control provides a means of decreasing the passage time as the speed of the flow increases.

	[[~~image~~:~~902.5.3.4.2~~.gif\|center\|thumb\|700px\|<center>'''Gap reduction settings and added initial time'''</center>]]		[[File:Gap reduction settings and added initial time.gif\|center\|thumb\|700px\|<center>'''Gap reduction settings and added initial time'''</center>]]

	The settings for gap reduction control are (terms may vary from brand to brand, consult controller manual for terminology):		The settings for gap reduction control are (terms may vary from brand to brand, consult controller manual for terminology):
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	:5. Added Initial. This setting allows the controller to increase the minimum green time to account for the vehicles stored between the detector and the stop bar at the beginning of the green interval. Without this setting, the minimum green would have to be set high enough to ensure all vehicles could clear the intersection. This time is set based on the number of seconds added for each detection while the phase is not green, usually 0.5 to one second added to the programmed minimum per actuation.		:5. Added Initial. This setting allows the controller to increase the minimum green time to account for the vehicles stored between the detector and the stop bar at the beginning of the green interval. Without this setting, the minimum green would have to be set high enough to ensure all vehicles could clear the intersection. This time is set based on the number of seconds added for each detection while the phase is not green, usually 0.5 to one second added to the programmed minimum per actuation.

	The benefit of these settings is best realized when stop bar detection is not used on the approach or is de-activated during the approach green interval.		The benefit of these settings is best realized when stop bar detection is not used on the approach or is de-activated during the approach green interval.

	===902.23.8.3 Detection on High-Speed Approaches===		===902.23.8.3 Detection on High-Speed Approaches===

RollerA: /* 902.23.7.3 Pedestrian Signal Timing */

2025-11-25T18:44:57Z

902.23.7.3 Pedestrian Signal Timing

← Older revision		Revision as of 13:44, 25 November 2025
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	[[File:Phase-Associated Pedestrian Operation.jpg\|frame\|center\|<center>'''Phase-Associated Pedestrian Operation'''</center>]]		[[File:Phase-Associated Pedestrian Operation.jpg\|frame\|center\|<center>'''Phase-Associated Pedestrian Operation'''</center>]]


	The pedestrian WALK and flashing DON'T WALK indications for northbound-southbound on the east side of the intersection would be displayed only during phase 6. Likewise, the indications for eastbound-westbound on the south side would be displayed only during phase 4.		The pedestrian WALK and flashing DON'T WALK indications for northbound-southbound on the east side of the intersection would be displayed only during phase 6. Likewise, the indications for eastbound-westbound on the south side would be displayed only during phase 4.
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	Under rare circumstances, an exclusive movement might be needed for the pedestrian indications.		Under rare circumstances, an exclusive movement might be needed for the pedestrian indications.

	Other options should be considered prior to the installation of an exclusive pedestrian movement.		Other options should be considered prior to the installation of an exclusive pedestrian movement.

	==902.23.8 Detector Settings==		==902.23.8 Detector Settings==

RollerA: /* 902.23.6 Overlaps and Right Turn Phasing */

2025-11-25T18:43:19Z

902.23.6 Overlaps and Right Turn Phasing

← Older revision		Revision as of 13:43, 25 November 2025
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	'''Support.''' An "overlap" provides a green or flashing yellow arrow indication for a traffic movement during the green intervals of two or more phases. The overlap green indication can be displayed during the change period between two or more phases if these phases are consecutive. Overlaps are also used to facilitate the operation of flashing yellow arrows for permissive turn movements. An overlap can be integrated into an actuated controller to supplement the flow of traffic. A simple application of an overlap is shown below:		'''Support.''' An "overlap" provides a green or flashing yellow arrow indication for a traffic movement during the green intervals of two or more phases. The overlap green indication can be displayed during the change period between two or more phases if these phases are consecutive. Overlaps are also used to facilitate the operation of flashing yellow arrows for permissive turn movements. An overlap can be integrated into an actuated controller to supplement the flow of traffic. A simple application of an overlap is shown below:

	[[~~image~~:~~902.5.2.3 OL&RTphasing~~.gif\|frame\|center\|<center>'''Simple Overlap Application'''</center>]]		[[File:Simple Overlap Application.gif\|frame\|center\|<center>'''Simple Overlap Application'''</center>]]

	For this case, a through movement is labeled "OLA" (OverLap A). OLA indication can be green while either phase 1 or phase 2 is green. While phase 1 is timing out the change period in transition to phase 2, the OLA indication remains green since OLA follows concurrently. OLA indication is red when phase 3 is green or yellow.		For this case, a through movement is labeled "OLA" (OverLap A). OLA indication can be green while either phase 1 or phase 2 is green. While phase 1 is timing out the change period in transition to phase 2, the OLA indication remains green since OLA follows concurrently. OLA indication is red when phase 3 is green or yellow.
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	Overlaps need not be used when normal NEMA dual ring structure can be utilized. In the previous example, the overlap is to be assigned to phase 6. A more practical application is for signalizing a right turn movement as shown below:		Overlaps need not be used when normal NEMA dual ring structure can be utilized. In the previous example, the overlap is to be assigned to phase 6. A more practical application is for signalizing a right turn movement as shown below:

	[[~~image~~:~~902.5.2.3 OL&RTphasing2~~.gif\|frame\|center\|<center>'''Practical Application for Signalizing a Right Turn'''</center>]]		[[File:Practical Application for Signalizing a Right Turn.gif\|frame\|center\|<center>'''Practical Application for Signalizing a Right Turn'''</center>]]

	In this case, the right turn phase is labeled "OLA" (Overlap A). OLA will display a green right while either phase 1 or phase 7 is green and will display a ball green when phase 2 and phase 6 are green. It receives no additional time, since its time comes from phases 1 and 7.		In this case, the right turn phase is labeled "OLA" (Overlap A). OLA will display a green right while either phase 1 or phase 7 is green and will display a ball green when phase 2 and phase 6 are green. It receives no additional time, since its time comes from phases 1 and 7.

RollerA: /* 902.23.4 Left Turn Lanes */

2025-11-25T18:41:17Z

902.23.4 Left Turn Lanes

← Older revision		Revision as of 13:41, 25 November 2025
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	Where the flow of the dual left turn lanes will carry traffic downstream must be taken into account. There is to be at least two through lanes of traffic of sufficient length to handle the completion of the dual turning lanes. Any lane reduction after a dual left turn is to take place far enough away from the intersection so as to provide adequate merging distances. Turning one lane of the dual left into another downstream turning lane is to be clearly signed in advance of the dual left turn.		Where the flow of the dual left turn lanes will carry traffic downstream must be taken into account. There is to be at least two through lanes of traffic of sufficient length to handle the completion of the dual turning lanes. Any lane reduction after a dual left turn is to take place far enough away from the intersection so as to provide adequate merging distances. Turning one lane of the dual left into another downstream turning lane is to be clearly signed in advance of the dual left turn.
	[[~~image~~:902.11.28.jpg\|left\|100px]]		[[File:Figure 902.23.1.jpg\|left\|100px]]

	=={{SpanID\|902.23.5}}902.23.5 Guidelines for Use of the Flashing Yellow Left Arrow (FYA)==		=={{SpanID\|902.23.5}}902.23.5 Guidelines for Use of the Flashing Yellow Left Arrow (FYA)==

RollerA: /* 902.23.3.4 Alternate Sequences */

2025-11-25T18:39:32Z

902.23.3.4 Alternate Sequences

← Older revision		Revision as of 13:39, 25 November 2025
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	In order to allow the northbound phase 1 to become a lagging left turn, the sequence of phase 1 and phase 2 must be programmed to switch. Under this alternate sequence, the ring structure would be:		In order to allow the northbound phase 1 to become a lagging left turn, the sequence of phase 1 and phase 2 must be programmed to switch. Under this alternate sequence, the ring structure would be:

	[[~~image~~:~~902.5.2.5~~ Alternate Sequence ~~ring~~.gif\|frame\|center\|<center>'''Alternate Sequence Ring'''</center>]]		[[File:Alternate Sequence Ring.gif\|frame\|center\|<center>'''Alternate Sequence Ring'''</center>]]

	This ring sequence starts with southbound left and through, and ends on the left side of the barrier with northbound left and through. Sequencing on the right side of the barrier is unchanged. More than one alternate sequence can be programmed.		This ring sequence starts with southbound left and through, and ends on the left side of the barrier with northbound left and through. Sequencing on the right side of the barrier is unchanged. More than one alternate sequence can be programmed.