902.23 Traffic Signal Phasing and Operation - Revision history

Hoskir: /* 902.23.1.2 Fully-actuated Control */ updated link

2026-03-02T19:28:57Z

902.23.1.2 Fully-actuated Control: updated link

← Older revision		Revision as of 14:28, 2 March 2026
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	The phases in an actuated controller can be assigned or grouped in many ways to provide unique operations that best serve the intersection's needs. The most common is the dual ring eight-phase configuration. This arrangement allows for separate through and left turn phases for up to four approaches. The opposing left turns are typically on concurrently, either leading or lagging. Through the software, the phases can be repositioned to provide a lead-lag left operation if so desired. Examples of typically used configurations are found in [http://sp/sites/sl/programdelivery/design/SignalsandLighting/Shared%20Documents/Signal_Phasing_and_Layout_Examples.pdf#search=signal%20phasing%20layout Signal Phasing and Layout Examples].		The phases in an actuated controller can be assigned or grouped in many ways to provide unique operations that best serve the intersection's needs. The most common is the dual ring eight-phase configuration. This arrangement allows for separate through and left turn phases for up to four approaches. The opposing left turns are typically on concurrently, either leading or lagging. Through the software, the phases can be repositioned to provide a lead-lag left operation if so desired. Examples of typically used configurations are found in [http://sp/sites/sl/programdelivery/design/SignalsandLighting/Shared%20Documents/Signal_Phasing_and_Layout_Examples.pdf#search=signal%20phasing%20layout Signal Phasing and Layout Examples].

	Efficient actuated operation is dependent on the type and placement of the detectors. Poor detector placement can have a serious impact on the delay and capacity of an intersection. Different types of detection are discussed in [[902.21_Designing_a_MoDOT_Traffic_Signal#902.21.7_Detectors\|EPG 902.21.7]] and [[902.26_Construction_Inspection_Guidelines_for_Sec_902#Detector_Installation_(for_Sec_902.13)\|EPG 902.26 - Detector Installation (for Sec 902.13)]]. Typically, stop bar presence detection is used. A common presence detector is a 6 ft. x 30 ft. area. Mainline through detection can be supplemented with advanced detectors located a distance from the stop bar based on the speed of approaching traffic.		Efficient actuated operation is dependent on the type and placement of the detectors. Poor detector placement can have a serious impact on the delay and capacity of an intersection. Different types of detection are discussed in [[902.21_Designing_a_MoDOT_Traffic_Signal#902.21.7_Detectors\|EPG 902.21.7 Detectors]] and [[902.26_Construction_Inspection_Guidelines_for_Sec_902#Detector_Installation_(for_Sec_902.13)\|EPG 902.26 - Detector Installation (for Sec 902.13)]]. Typically, stop bar presence detection is used. A common presence detector is a 6 ft. x 30 ft. area. Mainline through detection can be supplemented with advanced detectors located a distance from the stop bar based on the speed of approaching traffic.

	Full actuation and advance vehicle detection on high-speed approaches are typically used to reduce the frequency of vehicles in the “dilemma zone”. The dilemma zone is the area where the onset of the yellow change interval creates difficulty for the driver to decide whether to stop or proceed.		Full actuation and advance vehicle detection on high-speed approaches are typically used to reduce the frequency of vehicles in the “dilemma zone”. The dilemma zone is the area where the onset of the yellow change interval creates difficulty for the driver to decide whether to stop or proceed.

Hoskir: /* 902.23.1.2 Fully-actuated Control */ updated links

2026-02-23T14:51:04Z

902.23.1.2 Fully-actuated Control: updated links

← Older revision		Revision as of 09:51, 23 February 2026
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	The phases in an actuated controller can be assigned or grouped in many ways to provide unique operations that best serve the intersection's needs. The most common is the dual ring eight-phase configuration. This arrangement allows for separate through and left turn phases for up to four approaches. The opposing left turns are typically on concurrently, either leading or lagging. Through the software, the phases can be repositioned to provide a lead-lag left operation if so desired. Examples of typically used configurations are found in [http://sp/sites/sl/programdelivery/design/SignalsandLighting/Shared%20Documents/Signal_Phasing_and_Layout_Examples.pdf#search=signal%20phasing%20layout Signal Phasing and Layout Examples].		The phases in an actuated controller can be assigned or grouped in many ways to provide unique operations that best serve the intersection's needs. The most common is the dual ring eight-phase configuration. This arrangement allows for separate through and left turn phases for up to four approaches. The opposing left turns are typically on concurrently, either leading or lagging. Through the software, the phases can be repositioned to provide a lead-lag left operation if so desired. Examples of typically used configurations are found in [http://sp/sites/sl/programdelivery/design/SignalsandLighting/Shared%20Documents/Signal_Phasing_and_Layout_Examples.pdf#search=signal%20phasing%20layout Signal Phasing and Layout Examples].

	Efficient actuated operation is dependent on the type and placement of the detectors. Poor detector placement can have a serious impact on the delay and capacity of an intersection. Different types of detection are discussed in [[#902.5.~~7 Detectors~~\|EPG 902.5.7]] and [[902.~~15 Designing a Traffic Signal~~#~~902~~.~~15.3 Detectors~~\|EPG 902.15.3]]. Typically, stop bar presence detection is used. A common presence detector is a 6 ft. x 30 ft. area. Mainline through detection can be supplemented with advanced detectors located a distance from the stop bar based on the speed of approaching traffic.		Efficient actuated operation is dependent on the type and placement of the detectors. Poor detector placement can have a serious impact on the delay and capacity of an intersection. Different types of detection are discussed in [[902.21_Designing_a_MoDOT_Traffic_Signal#902.21.7_Detectors\|EPG 902.21.7]] and [[902.26_Construction_Inspection_Guidelines_for_Sec_902#Detector_Installation_(for_Sec_902.13)\|EPG 902.26 - Detector Installation (for Sec 902.13)]]. Typically, stop bar presence detection is used. A common presence detector is a 6 ft. x 30 ft. area. Mainline through detection can be supplemented with advanced detectors located a distance from the stop bar based on the speed of approaching traffic.

	Full actuation and advance vehicle detection on high-speed approaches are typically used to reduce the frequency of vehicles in the “dilemma zone”. The dilemma zone is the area where the onset of the yellow change interval creates difficulty for the driver to decide whether to stop or proceed.		Full actuation and advance vehicle detection on high-speed approaches are typically used to reduce the frequency of vehicles in the “dilemma zone”. The dilemma zone is the area where the onset of the yellow change interval creates difficulty for the driver to decide whether to stop or proceed.

Hoskir: /* 902.23.3.4 Alternate Sequences */ removed link not needed

2026-02-23T14:47:38Z

902.23.3.4 Alternate Sequences: removed link not needed

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	===902.23.3.4 Alternate Sequences===		===902.23.3.4 Alternate Sequences===

	'''Support.''' When needed, the normal NEMA ring sequence can be altered to fit operating conditions, with restrictions as detailed in ~~[[#902.23.3 Signal Phasing\|~~EPG 902.23.3]]. The most common application is to provide lead-lag left turns. Assume this phasing assignment for the following intersection:		'''Support.''' When needed, the normal NEMA ring sequence can be altered to fit operating conditions, with restrictions as detailed in EPG 902.23.3. The most common application is to provide lead-lag left turns. Assume this phasing assignment for the following intersection:

	[[File:Alternate Sequence.gif\|frame\|center\|<center>'''Alternate Sequence'''</center>]]		[[File:Alternate Sequence.gif\|frame\|center\|<center>'''Alternate Sequence'''</center>]]

Hoskir: /* 902.23.7.1.2 Maximum Green */ updated link

2026-02-23T14:44:35Z

902.23.7.1.2 Maximum Green: updated link

← Older revision		Revision as of 09:44, 23 February 2026
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	'''Support.''' Controllers allow for different maximum settings to be enacted through the time clock. This is useful if heavy demand on a certain phase can be accurately predicted and set to a time of day. This is also useful with semi-actuated control where the mainline timing is controlled by a maximum recall since mainline demand typically changes by time of day. Controller clocks should be set by a central signal system if utilized; however, if there is not a central signal system it is recommended to set the controller clock using www.time.gov to remain consistent.		'''Support.''' Controllers allow for different maximum settings to be enacted through the time clock. This is useful if heavy demand on a certain phase can be accurately predicted and set to a time of day. This is also useful with semi-actuated control where the mainline timing is controlled by a maximum recall since mainline demand typically changes by time of day. Controller clocks should be set by a central signal system if utilized; however, if there is not a central signal system it is recommended to set the controller clock using www.time.gov to remain consistent.

	'''Guidance.''' Although the concept of a cycle length is usually reserved for pre-timed control and coordinated actuated control, it can be applied to isolated, actuated control. The temptation to set all maximums at an isolated intersection extremely high should be avoided. Maximum settings too high result in longer delay for other approaches and defeat the flexibility of actuated control by creating needless backups. See [[#902.23.~~5 Coordination~~\|EPG 902.23.5 Coordination]] for more discussion on cycle lengths for all types of control.		'''Guidance.''' Although the concept of a cycle length is usually reserved for pre-timed control and coordinated actuated control, it can be applied to isolated, actuated control. The temptation to set all maximums at an isolated intersection extremely high should be avoided. Maximum settings too high result in longer delay for other approaches and defeat the flexibility of actuated control by creating needless backups. See [[902.23_Traffic_Signal_Phasing_and_Operation#902.23.11_Coordination\|EPG 902.23.11 Coordination]] for more discussion on cycle lengths for all types of control.

	===902.23.7.2 Yellow Change and Red Clearance Intervals===		===902.23.7.2 Yellow Change and Red Clearance Intervals===

Hoskir: /* 902.23.12 Controller Assembly Components */ updated link

2026-02-23T14:42:32Z

902.23.12 Controller Assembly Components: updated link

← Older revision		Revision as of 09:42, 23 February 2026
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	===902.23.12.1 Controller Unit ===		===902.23.12.1 Controller Unit ===

	'''Support.''' The controller unit (CU) is a solid-state traffic actuated unit. The CU interfaces with a number of low voltage (logic level) input and output functions to control signal lamps, receive inputs from detectors, operate in coordinated systems, etc. Additional information on types of control is found in [[#902.5.~~2 Traffic Signal Operation~~\|EPG 902.5.2 Traffic Signal Operation]].		'''Support.''' The controller unit (CU) is a solid-state traffic actuated unit. The CU interfaces with a number of low voltage (logic level) input and output functions to control signal lamps, receive inputs from detectors, operate in coordinated systems, etc. Additional information on types of control is found in [[902.23_Traffic_Signal_Phasing_and_Operation#902.23.1_Traffic_Signal_Operation\|EPG 902.23.1 Traffic Signal Operation]].

	<u>NEMA TS1</u>		<u>NEMA TS1</u>
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	===902.23.12.5 Detector Interface ===		===902.23.12.5 Detector Interface ===

	'''Support.''' The detector interface provides connections between the CU and the detection devices. In solid-state pre-timed and NEMA TS1 controllers, the connections are made through the back panel. In NEMA TS2 controllers, the detector inputs and outputs are linked to the CU through a BIU. In Type 170/2070 cabinets, the input file serves as the detector interface.		'''Support.''' The detector interface provides connections between the CU and the detection devices. In solid-state pre-timed and NEMA TS1 controllers, the connections are made through the back panel. In NEMA TS2 controllers, the detector inputs and outputs are linked to the CU through a BIU. In Type 170/2070 cabinets, the input file serves as the detector interface.

	=={{SpanID\|902.23.13}}902.23.13 Detectors==		=={{SpanID\|902.23.13}}902.23.13 Detectors==

Hoskir: /* 902.23.11.2.4.2 Phase Sequence */ updated link

2026-02-23T14:40:10Z

902.23.11.2.4.2 Phase Sequence: updated link

← Older revision		Revision as of 09:40, 23 February 2026
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	=====902.23.11.2.4.2 Phase Sequence=====		=====902.23.11.2.4.2 Phase Sequence=====

	'''Guidance.''' When more than two phases are used, the sequence in which the indications are displayed must be determined for each timing plan. The usual choice is when to display a protected left turn in relation to the mainline green: at the start (lead) or the end (lag). The use of lead-lag for protected left turns on the mainline can greatly affect the progression. (See [[#902.5.27.~~1 Leading and Lagging Left~~-Turns\|EPG 902.5.27.1 Leading and Lagging Left-Turns]].)		'''Guidance.''' When more than two phases are used, the sequence in which the indications are displayed must be determined for each timing plan. The usual choice is when to display a protected left turn in relation to the mainline green: at the start (lead) or the end (lag). The use of lead-lag for protected left turns on the mainline can greatly affect the progression. (See [[902.23_Traffic_Signal_Phasing_and_Operation#902.23.3.2_Leading_and_Lagging_Left-Turns\|EPG 902.23.3.2 Leading and Lagging Left-Turns]].)

	If optimization software is being used, the program will generally give a mainline sequence at each intersection that maximizes the green band. Side street sequencing is usually left up to the user. There might be some timing plans where the side street sequence becomes a factor in coordination. A heavy left turn onto the mainline might call for a sequence that puts the side street left turn indications at a point in the cycle that allows for the group to clear a downstream intersection.		If optimization software is being used, the program will generally give a mainline sequence at each intersection that maximizes the green band. Side street sequencing is usually left up to the user. There might be some timing plans where the side street sequence becomes a factor in coordination. A heavy left turn onto the mainline might call for a sequence that puts the side street left turn indications at a point in the cycle that allows for the group to clear a downstream intersection.

	====902.23.11.2.5 Determine Offsets and Transition in Each Timing Plan====		====902.23.11.2.5 Determine Offsets and Transition in Each Timing Plan====

Hoskir: /* {{SpanID|902.23.10}}902.23.10 Control Features for Non-coordinated Signals */

2026-02-23T14:30:55Z

{{SpanID|902.23.10}}902.23.10 Control Features for Non-coordinated Signals

← Older revision		Revision as of 09:30, 23 February 2026
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	:Many actuated controllers also have a feature called “soft recall” that allows the selected phase to be serviced only if there are no other conflicting calls. This feature can be used on the main street during periods of light traffic. The advantage over minimum recall is the controller can skip servicing the main street, if no real calls exist, and move on to the next called phase. This can provide a quicker response during the periods of light traffic.		:Many actuated controllers also have a feature called “soft recall” that allows the selected phase to be serviced only if there are no other conflicting calls. This feature can be used on the main street during periods of light traffic. The advantage over minimum recall is the controller can skip servicing the main street, if no real calls exist, and move on to the next called phase. This can provide a quicker response during the periods of light traffic.

	:For more information about Recall Phases refer to [[902.23_Traffic_Signal_Phasing_and_Operation#902.23.8.6_Recalled_Phases\|EPG 902.23.8.6].		:For more information about Recall Phases refer to [[902.23_Traffic_Signal_Phasing_and_Operation#902.23.8.6_Recalled_Phases\|EPG 902.23.8.6]].

	=={{SpanID\|902.23.11}}902.23.11 Coordination==		=={{SpanID\|902.23.11}}902.23.11 Coordination==

Hoskir: /* {{SpanID|902.23.10}}902.23.10 Control Features for Non-coordinated Signals */ updated links

2026-02-23T14:30:35Z

{{SpanID|902.23.10}}902.23.10 Control Features for Non-coordinated Signals: updated links

← Older revision		Revision as of 09:30, 23 February 2026
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	:Gap reduction which allows the passage time to decrease as the speed of the flow increases is another setting commonly used at locations with advance detection.		:Gap reduction which allows the passage time to decrease as the speed of the flow increases is another setting commonly used at locations with advance detection.

	:Features of density control are discussed in [[#902.5.37.~~2 Advance Detectors and Gap Reduction~~\|EPG 902.5.37.2]].		:Features of density control are discussed in [[902.23_Traffic_Signal_Phasing_and_Operation#902.23.8.2_Advance_Detectors_and_Gap_Reduction\|EPG 902.23.8.2]].

	:'''3. Recall Operation.''' Each phase of a controller is equipped with a recall feature. With recall disabled, the phase responds only to its detectors. With recall enabled, the controller can place a call to service that phase without vehicles being detected. This is accomplished by the controller placing a single call back to the phase when the clearance interval is initiated.		:'''3. Recall Operation.''' Each phase of a controller is equipped with a recall feature. With recall disabled, the phase responds only to its detectors. With recall enabled, the controller can place a call to service that phase without vehicles being detected. This is accomplished by the controller placing a single call back to the phase when the clearance interval is initiated.
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	:Many actuated controllers also have a feature called “soft recall” that allows the selected phase to be serviced only if there are no other conflicting calls. This feature can be used on the main street during periods of light traffic. The advantage over minimum recall is the controller can skip servicing the main street, if no real calls exist, and move on to the next called phase. This can provide a quicker response during the periods of light traffic.		:Many actuated controllers also have a feature called “soft recall” that allows the selected phase to be serviced only if there are no other conflicting calls. This feature can be used on the main street during periods of light traffic. The advantage over minimum recall is the controller can skip servicing the main street, if no real calls exist, and move on to the next called phase. This can provide a quicker response during the periods of light traffic.

	:For more information about Recall Phases refer to [~~https://epg.modot.org/index.php/~~902.~~5_Traffic_Control_Signal_Features_(MUTCD_Chapter_4D)~~#902.5.37.6_Recalled_Phases EPG 902.5.37.6].		:For more information about Recall Phases refer to [[902.23_Traffic_Signal_Phasing_and_Operation#902.23.8.6_Recalled_Phases\|EPG 902.23.8.6].

	=={{SpanID\|902.23.11}}902.23.11 Coordination==		=={{SpanID\|902.23.11}}902.23.11 Coordination==

Hoskir: moved menu to right

2026-01-22T19:33:22Z

moved menu to right

← Older revision		Revision as of 14:33, 22 January 2026
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			<div style="float: right; width: 550px; margin-top: 5px; margin-left: 30px; margin-bottom: 30px;">__TOC__</div>
	==902.23.1 Traffic Signal Operation==		==902.23.1 Traffic Signal Operation==

Hoskir: /* {{SpanID|902.23.9}}902.23.9 Power Outages at Signalized Intersections */ updated per RR 4060

2026-01-22T19:31:28Z

{{SpanID|902.23.9}}902.23.9 Power Outages at Signalized Intersections: updated per RR 4060

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