Part 4. Highway Traffic Signals

TABLE OF CONTENTS
CHAPTER 4A	GENERAL
Section 4A.01	Types
Section 4A.02	Definitions Relating to Highway Traffic Signals

CHAPTER 4B	TRAFFIC CONTROL SIGNALS—GENERAL
Section 4B.01	General
Section 4B.02	Basis of Installation or Removal of Traffic Control Signals
Section 4B.03	Advantages and Disadvantages of Traffic Control Signals
Section 4B.04	Alternatives to Traffic Control Signals
Section 4B.05	Adequate Roadway Capacity

CHAPTER 4C	TRAFFIC CONTROL SIGNAL NEEDS STUDIES
Section 4C.01	Studies and Factors for Justifying Traffic Control Signals
Section 4C.02	Warrant 1, Eight-Hour Vehicular Volume
Section 4C.03	Warrant 2, Four-Hour Vehicular Volume
Section 4C.04	Warrant 3, Peak Hour
Section 4C.05	Warrant 4, Pedestrian Volume
Section 4C.06	Warrant 5, School Crossing
Section 4C.07	Warrant 6, Coordinated Signal System
Section 4C.08	Warrant 7, Crash Experience
Section 4C.09	Warrant 8, Roadway Network

CHAPTER 4D	TRAFFIC CONTROL SIGNAL FEATURES
Section 4D.01	General
Section 4D.02	Responsibility for Operation and Maintenance
Section 4D.03	Provisions for Pedestrians
Section 4D.04	Meaning of Vehicular Signal Indications
Section 4D.05	Application of Steady Signal Indications
Section 4D.06	Application of Steady Signal Indications for Left Turns
Section 4D.07	Application of Steady Signal Indications for Right Turns
Section 4D.08	Prohibited Steady Signal Indications
Section 4D.09	Unexpected Conflicts During Green or Yellow Intervals
Section 4D.10	Yellow Change and Red Clearance Intervals
Section 4D.11	Application of Flashing Signal Indications
Section 4D.12	Flashing Operation of Traffic Control Signals
Section 4D.13	Preemption and Priority Control of Traffic Control Signals
Section 4D.14	Coordination of Traffic Control Signals
Section 4D.15	Size, Number, and Location of Signal Faces by Approach
Section 4D.16	Number and Arrangement of Signal Sections in Vehicular Traffic Control Signal Faces
Section 4D.17	Visibility, Shielding, and Positioning of Signal Faces
Section 4D.18	Design, Illumination, and Color of Signal Sections
Section 4D.19	Lateral Placement of Signal Supports and Cabinets
Section 4D.20	Temporary Traffic Control Signals
Section 4D.21	Traffic Signal Signs, Auxiliary

FIGURES
CHAPTER 4C	TRAFFIC CONTROL SIGNAL NEEDS STUDIES
Figure 4C-1	Warrant 2, Four-Hour Vehicular Volume
Figure 4C-2	Warrant 2, Four-Hour Vehicular Volume (70% Factor)
Figure 4C-3	Warrant 3, Peak Hour
Figure 4C-4	Warrant 3, Peak Hour (70% Factor)

CHAPTER 4D	TRAFFIC CONTROL SIGNAL FEATURES
Figure 4D-1	Maximum Mounting Height of Signal Faces Located Between 12 m (40 ft) and 16 m (53 ft) from Stop Line
Figure 4D-2	Horizontal Location of Signal Faces
Figure 4D-3	Typical Arrangements of Signal Lenses in Signal Faces

TABLES
CHAPTER 4C	TRAFFIC CONTROL SIGNAL NEEDS STUDIES
Table 4C-1	Warrant 1, Eight-Hour Vehicular Volume

CHAPTER 4D	TRAFFIC CONTROL SIGNAL FEATURES
Table 4D-1	Minimum Sight Distance

CHAPTER 4A. GENERAL

Section 4A.01 Types

Support:
The following types and uses of highway traffic signals are discussed in Part 4: traffic control signals; pedestrian signals; emergency-vehicle traffic control signals; traffic control signals for one-lane, two-way facilities; traffic control signals for freeway entrance ramps; traffic control signals for movable bridges; lane-use control signals; flashing beacons; and in-roadway lights.

Section 4A.02 Definitions Relating to Highway Traffic Signals

Standard:
The following technical terms, when used in Part 4, shall be defined as follows:

Accessible Pedestrian Signal—a device that communicates information about pedestrian timing in nonvisual format such as audible tones, verbal messages, and/or vibrating surfaces.
Active Grade Crossing Warning System—the flashing-light signals, with or without warning gates, together with the necessary control equipment used to inform road users of the approach or presence of trains at highway-rail grade crossings.
Actuated Operation—a type of traffic control signal operation in which some or all signal phases are operated on the basis of actuation.
Actuation—initiation of a change in or extension of a traffic signal phase through the operation of any type of detector.
Approach—all lanes of traffic moving towards an intersection or a midblock location from one direction, including any adjacent parking lane(s).
Average Day—a day representing traffic volumes normally and repeatedly found at a location, typically a weekday when volumes are influenced by employment or a weekend when volumes are influenced by entertainment or recreation.
Backplate—a thin strip of material that extends outward from and parallel to a signal face on all sides of a signal housing to provide a background for improved visibility of the signal indications.
Beacon—a highway traffic signal with one or more signal sections that operates in a flashing mode.
Conflict Monitor—a device used to detect and respond to improper or conflicting signal indications and improper operating voltages in a traffic controller assembly.
Controller Assembly—a complete electrical device mounted in a cabinet for controlling the operation of a highway traffic signal.
Controller Unit—that part of a controller assembly that is devoted to the selection and timing of the display of signal indications.
Crosswalk—(a) that part of a roadway at an intersection included within the connections of the lateral lines of the sidewalks on opposite sides of the highway measured from the curbs or in the absence of curbs, from the edges of the traversable roadway, and in the absence of a sidewalk on one side of the roadway, the part of a roadway included within the extension of the lateral lines of the sidewalk at right angles to the centerline; (b) any portion of a roadway at an intersection or elsewhere distinctly indicated for pedestrian crossing by lines or other markings on the surface.
Cycle Length—the time required for one complete sequence of signal indications.
Dark Mode—the lack of all signal indications at a signalized location. (The dark mode is most commonly associated with power failures, ramp meters, beacons, and some movable bridge signals.)
Detector—a sensing device used for determining the presence or passage of vehicles or pedestrians.
Emergency Vehicle Traffic Control Signal—a special traffic control signal that assigns the right-of-way to an authorized emergency vehicle.
Flasher—a device used to turn highway traffic signal indications on and off at a repetitive rate of approximately once per second.
Flashing (Flashing Mode)—a mode of operation in which a traffic signal indication is turned on and off repetitively.
Full-Actuated Operation—a type of traffic control signal operation in which all signal phases function on the basis of actuation.
Highway Traffic Signal—a power-operated traffic control device by which traffic is warned or directed to take some specific action. These devices do not include power-operated signs, illuminated pavement markers, barricade warning lights, or steady-burning electric lamps.
In-Roadway Lights—a special type of highway traffic signal installed in the roadway surface to warn road users that they are approaching a condition on or adjacent to the roadway that might not be readily apparent and might require the road users to slow down and/or come to a stop.
Intersection—(a) the area embraced within the prolongation or connection of the lateral curb lines, or if none, the lateral boundary lines of the roadways of two highways that join one another at, or approximately at, right angles, or the area within which vehicles traveling on different highways that join at any other angle may come into conflict; (b) the junction of an alley or driveway with a roadway or highway shall not constitute an intersection.
Intersection Control Beacon—a beacon used only at an intersection to control two or more directions of travel.
Interval—the part of a signal cycle during which signal indications do not change.
Interval Sequence—the order of appearance of signal indications during successive intervals of a signal cycle.
Lane-Use Control Signal—a signal face displaying signal indications to permit or prohibit the use of specific lanes of a roadway or to indicate the impending prohibition of such use.
Lens—see Signal Lens.
Louver—a device that can be mounted inside a signal visor to restrict visibility of a signal indication from the side or to limit the visibility of the signal indication to a certain lane or lanes.
Major Street—the street normally carrying the higher volume of vehicular traffic.
Malfunction Management Unit—same as Conflict Monitor.
Minor Street—the street normally carrying the lower volume of vehicular traffic.
Movable Bridge Resistance Gate—a type of traffic gate, which is located downstream of the movable bridge warning gate, that provides a physical deterrent to vehicle and/or pedestrian traffic when placed in the appropriate position.
Movable Bridge Warning Gate—a type of traffic gate designed to warn, but not primarily to block, vehicle and/or pedestrian traffic when placed in the appropriate position.
Pedestrian Change Interval—an interval during which the flashing UPRAISED HAND (symbolizing DONT WALK) signal indication is displayed. When a verbal message is provided at an accessible pedestrian signal, the verbal message is "wait."
Pedestrian Clearance Time—the time provided for a pedestrian crossing in a crosswalk, after leaving the curb or shoulder, to travel to the center of the farthest traveled lane or to a median.
Pedestrian Signal Head—a signal head, which contains the symbols WALKING PERSON (symbolizing WALK) and UPRAISED HAND (symbolizing DONT WALK), that is installed to direct pedestrian traffic at a traffic control signal.
Permissive Mode—a mode of traffic control signal operation in which, when a CIRCULAR GREEN signal indication is displayed, left or right turns may be made after yielding to pedestrians and/or oncoming traffic.
Platoon—a group of vehicles or pedestrians traveling together as a group, either voluntarily or involuntarily, because of traffic signal controls, geometrics, or other factors.
Preemption Control—the transfer of normal operation of a traffic control signal to a special control mode of operation.
Pretimed Operation—a type of traffic control signal operation in which none of the signal phases function on the basis of actuation.
Priority Control—a means by which the assignment of right-of-way is obtained or modified.
Protected Mode—a mode of traffic control signal operation in which left or right turns may be made when a left or right GREEN ARROW signal indication is displayed.
Pushbutton—a button to activate pedestrian timing.
Pushbutton Locator Tone—a repeating sound that informs approaching pedestrians that they are required to push a button to actuate pedestrian timing and that enables pedestrians who have visual disabilities to locate the pushbutton.
Ramp Control Signal—a highway traffic signal installed to control the flow of traffic onto a freeway at an entrance ramp or at a freeway-to-freeway ramp connection.
Ramp Meter—see Ramp Control Signal.
Red Clearance Interval—an optional interval that follows a yellow change interval and precedes the next conflicting green interval.
Right-of-Way (Assignment)—the permitting of vehicles and/or pedestrians to proceed in a lawful manner in preference to other vehicles or pedestrians by the display of signal indications.
Roadway Network—a geographical arrangement of intersecting roadways.
Semiactuated Operation—a type of traffic control signal operation in which at least one, but not all, signal phases function on the basis of actuation.
Signal Coordination—the establishment of timed relationships between adjacent traffic control signals.
Signal Face—the front part of a signal head.
Signal Head—an assembly of one or more signal faces together with the associated signal housings.
Signal Housing—that part of a signal section that protects the light source and other required components.
Signal Indication—the illumination of a signal lens or equivalent device.
Signal Lens—that part of the signal section that redirects the light coming directly from the light source and its reflector, if any.
Signal Phase—the right-of-way, yeow change, and red clearance intervals in a cycle that are assigned to an independent traffic movement or combination of movements.
Signal Section—the assembly of a signal housing, signal lens, and light source with necessary components to be used for providing one signal indication.
Signal System—two or more traffic control signals operating in signal coordination.
Signal Timing—the amount of time allocated for the display of a signal indication.
Signal Visor—that part of a signal section that directs the signal indication specifically to approaching traffic and reduces the effect of direct external light entering the signal lens.
Signal Warrant—a threshold condition that, if found to be satisfied as part of an engineering study, shall result in analysis of other traffic conditions or factors to determine whether a traffic control signal or other improvement is justified.
Speed Limit Sign Beacon—a beacon used to supplement a SPEED LIMIT sign.
Steady (Steady Mode)—the continuous illumination of a signal indication for the duration of an interval, signal phase, or consecutive signal phases.
Stop Beacon—a beacon used to supplement a STOP sign, a DO NOT ENTER sign, or a WRONG WAY sign.
Traffic Control Signal (Traffic Signal)—any highway traffic signal by which traffic is alternately directed to stop and permitted to proceed.
Vibrotactile Pedestrian Device—a device that communicates, by touch, information about pedestrian timing using a vibrating surface.
Visibility-Limited Signal Face or Signal Section—a type of signal face or signal section designed to restrict the visibility of a signal indication from the side, to a certain lane or lanes, or to a certain distance from the stop line.
Walk Interval—an interval during which the WALKING PERSON (symbolizing WALK) signal indication is displayed. When a verbal message is provided at an accessible pedestrian signal, the verbal message is "walk sign."
Warning Beacon—a beacon used only to supplement an appropriate warning or regulatory sign or marker.
Yellow Change Interval—the first interval following the green interval during which the yellow signal indication is displayed.

Return to Part 4 Table of Contents

CHAPTER 4B. TRAFFIC CONTROL SIGNALS—GENERAL

Section 4B.01 General

Standard:
A traffic control signal (traffic signal) shall be defined as any highway traffic signal by which traffic is alternately directed to stop and permitted to proceed.

Traffic shall be defined as pedestrians, bicyclists, ridden or herded animals, vehicles, streetcars, and other conveyances either singularly or together while using any highway for purposes of travel.

Support:
Words such as pedestrians and bicyclists are used redundantly in selected sections of Part 4 to encourage sensitivity to these elements of "traffic."

Standards for traffic control signals are important because traffic control signals need to attract the attention of virtually every road user, including those who are older, those with impaired vision who meet legal requirements, as well as those who are fatigued or distracted, or who are not expecting to encounter a signal at a particular location. Standards for traffic control signals are also important because signals need to function reliably under a wide range of conditions including day and night, adverse weather, and visually complex surroundings.

Section 4B.02 Basis of Installation or Removal of Traffic Control Signals

Guidance:
The selection and use of traffic control signals should be based on an engineering study of roadway, pedestrian, bicyclist, and other conditions.

Support:
A careful analysis of traffic operations, pedestrian, and bicyclist needs, and other factors at a large number of signalized and unsignalized intersections, coupled with engineering judgment, has provided a series of signal warrants, described in Chapter 4C, that define the minimum conditions under which installing traffic control signals might be justified.

Guidance:
If changes in traffic patterns eliminate the need for a traffic control signal, consideration should be given to removing it and replacing it with appropriate alternative traffic control devices, if any are needed.

Option:
If the engineering study indicates that the traffic control signal is no longer justified, removal may be accomplished using the following steps:

Determine the appropriate traffic control to be used after removal of the signal.
Remove any sight-distance restrictions as necessary.
Inform the public of the removal study, for example by installing an informational sign (or signs) with the legend TRAFFIC SIGNAL UNDER STUDY FOR REMOVAL at the signalized location in a position where it is visible to all road users.
Flash or cover the signal heads for a minimum of 90 days, and install the appropriate stop control or other traffic control devices.
Remove the signal if the engineering data collected during the removal study period confirms that the signal is no longer needed. Instead of total removal of the traffic control signal, the poles and cables may remain in place for 1 year after removal of the signal heads for continued analysis.

Section 4B.03 Advantages and Disadvantages of Traffic Control Signals

Support:
When properly used, traffic control signals are valuable devices for the control of vehicular and pedestrian traffic. They assign the right-of-way to the various traffic movements and thereby profoundly influence traffic flow.

Traffic control signals that are properly designed, located, operated, and maintained will have one or more of the following advantages:

They provide for the orderly movement of traffic.
They increase the traffic-handling capacity of the intersection if proper physical layouts and control measures are used, and if the signal timing is reviewed and updated on a regular basis (every 2 years) to ensure that it satisfies current traffic demands.
They reduce the frequency and severity of certain types of crashes, especially right-angle collisions.
They are coordinated to provide for continuous or nearly continuous movement of traffic at a definite speed along a given route under favorable conditions.
They are used to interrupt heavy traffic at intervals to permit other traffic, vehicular or pedestrian, to cross.

Traffic control signals are often considered a panacea for all traffic problems at intersections. This belief has led to traffic control signals being installed at many locations where they are not needed, adversely affecting the safety and efficiency of vehicular, bicycle, and pedestrian traffic.

Traffic control signals, even when justified by traffic and roadway conditions, can be ill-designed, ineffectively placed, improperly operated, or poorly maintained. Improper or unjustified traffic control signals can result in one or more of the following disadvantages:

Excessive delay;
Excessive disobedience of the signal indications;
Increased use of less adequate routes as road users attempt to avoid the traffic control signals; and
Significant increases in the frequency of collisions (especially rear-end collisions).

Engineering studies of operating traffic control signals should be made to determine whether the type of installation and the timing program meet the current requirements of traffic.

Section 4B.04 Alternatives to Traffic Control Signals

Guidance:
Since vehicular delay and the frequency of some types of crashes are sometimes greater under traffic signal control than under STOP sign control, consideration should be given to providing alternatives to traffic control signals even if one or more of the signal warrants has been satisfied.

Option:
These alternatives may include, but are not limited to, the following:

Installing signs along the major street to warn road users approaching the intersection;
Relocating the stop line(s) and making other changes to improve the sight distance at the intersection;
Installing measures designed to reduce speeds on the approaches;
Installing a flashing beacon at the intersection to supplement STOP sign control;
Installing flashing beacons on warning signs in advance of a STOP sign controlled intersection on major- and/or minor-street approaches;
Adding one or more lanes on a minor-street approach to reduce the number of vehicles per lane on the approach;
Revising the geometrics at the intersection to channelize vehicular movements and reduce the time required for a vehicle to complete a movement, which could also assist pedestrians;
Installing roadway lighting if a disproportionate number of crashes occur at night;
Restricting one or more turning movements, perhaps on a time-of-day basis, if alternate routes are available;
If the warrant is satisfied, installing multiway STOP sign control;
Installing a roundabout; and
Employing other alternatives, depending on conditions at the intersection.

Section 4B.05 Adequate Roadway Capacity

Support:
The delays inherent in the alternating assignment of right-of-way at intersections controlled by traffic control signals can frequently be reduced by widening the major roadway, the minor roadway, or both roadways. Widening the minor roadway often benefits the operations on the major roadway, because it reduces the green time that must be assigned to minor-roadway traffic. In urban areas, the effect of widening can be achieved by eliminating parking on intersection approaches. It is desirable to have at least two lanes for moving traffic on each approach to a signalized intersection. Additional width on the departure side of the intersection, as well as on the approach side, will sometimes be needed to clear traffic through the intersection effectively.

Guidance:
Adequate roadway capacity should be provided at a signalized location. Before an intersection is widened, the additional green time pedestrians need to cross the widened roadways should be considered to ensure that it will not exceed the green time saved through improved vehicular flow.

Return to Part 4 Table of Contents

CHAPTER 4C. TRAFFIC CONTROL SIGNAL NEEDS STUDIES

Section 4C.01 Studies and Factors for Justifying Traffic Control Signals

Standard:
An engineering study of traffic conditions, pedestrian characteristics, and physical characteristics of the location shall be performed to determine whether installation of a traffic control signal is justified at a particular location.

The investigation of the need for a traffic control signal shall include an analysis of the applicable factors contained in the following traffic signal warrants and other factors related to existing operation and safety at the study location:

Warrant 1, Eight-Hour Vehicular Volume.
Warrant 2, Four-Hour Vehicular Volume.
Warrant 3, Peak Hour.
Warrant 4, Pedestrian Volume.
Warrant 5, School Crossing.
Warrant 6, Coordinated Signal System.
Warrant 7, Crash Experience.
Warrant 8, Roadway Network.

The satisfaction of a traffic signal warrant or warrants shall not in itself require the installation of a traffic control signal.

Support:
Sections 8D.07 and 10D.05 contain information regarding the use of traffic control signals instead of gates and/or flashing light signals at highway-railroad grade crossings and highway light rail transit grade crossings, respectively.

Guidance:
A traffic control signal should not be installed unless one or more of the factors described in this section are met.

A traffic control signal should not be installed unless an engineering study indicates that installing a traffic control signal will improve the overall safety and/or operation of the intersection.

A traffic control signal should not be installed if it will seriously disrupt progressive traffic flow.

The study should consider the effects of the right-turn vehicles from the minor-street approaches. Engineering judgment should be used to determine what, if any, portion of the right-turn traffic is subtracted from the minor-street traffic count when evaluating the count against the above signal warrants.

Engineering judgment should also be used in applying various traffic signal warrants to cases where approaches consist of one lane plus one left-turn or right-turn lane. The site-specific traffic characteristics dictate whether an approach should be considered as one lane or two lanes. For example, for an approach with one lane for through and right-turning traffic plus a left-turn lane, engineering judgment could indicate that it should be considered a one-lane approach if the traffic using the left-turn lane is minor. In such a case, the total traffic volume approaching the intersection should be applied against the signal warrants as a one-lane approach. The approach should be considered two lanes if approximately half of the traffic on the approach turns left and the left-turn lane is of sufficient length to accommodate all left-turn vehicles.

Similar engineering judgment and rationale should be applied to a street approach with one lane plus a right-turn lane. In this case, the degree of conflict of minor-street right-turn traffic with traffic on the major street should be considered. Thus, right-turn traffic should not be included in the minor-street volume if the movement enters the major street with minimal conflict. The approach should be evaluated as a one-lane approach with only the traffic volume in the through/left-turn lane considered.

At a location that is under development or construction and where it is not possible to obtain a traffic count that would represent future traffic conditions, hourly volumes should be estimated as part of an engineering study for comparison with traffic signal warrants.

For signal warrant analysis, a location with a wide median should be considered as one intersection.

Option:
Engineering study data may include the following:

The number of vehicles entering the intersection in each hour from each approach during 12 hours of an average day. It is desirable that the hours selected contain the greatest percentage of the 24-hour traffic volume.
Vehicular volumes for each traffic movement from each approach, classified by vehicle type (heavy trucks, passenger cars and light trucks, public-transit vehicles, and, in some locations, bicycles), during each 15-minute period of the 2 hours in the morning and 2 hours in the afternoon during which total traffic entering the intersection is greatest.
Pedestrian volume counts on each crosswalk during the same periods as the vehicular counts in Paragraph B above and during hours of highest pedestrian volume. Where young, elderly, and/or persons with physical or visual disabilities need special consideration, the pedestrians and their crossing times may be classified by general observation.
Information about nearby facilities and activity centers that serve the young, elderly, and/or persons with disabilities, including requests from persons with disabilities for accessible crossing improvements at the location under study. These persons may not be adequately reflected in the pedestrian volume count if the absence of a signal restrains their mobility.
The posted or statutory speed limit or the 85th-percentile speed on the uncontrolled approaches to the location.
A condition diagram showing details of the physical layout, including such features as intersection geometrics, channelization, grades, sight-distance restrictions, transit stops and routes, parking conditions, pavement markings, roadway lighting, driveways, nearby railroad crossings, distance to nearest traffic control signals, utility poles and fixtures, and adjacent land use.
A collision diagram showing crash experience by type, location, direction of movement, severity, weather, time of day, date, and day of week for at least 1 year.

The following data, which are desirable for a more precise understanding of the operation of the intersection, may be obtained during the periods specified in Paragraph B above:

Vehicle-hours of stopped time delay determined separately for each approach to be consistent with the Peak Hour Warrant.
The number and distribution of acceptable gaps in vehicular traffic on the major street for entrance from the minor street.
The posted or statutory speed limit or the 85th-percentile speed on controlled approaches at a point near to the intersection but unaffected by the control.
Pedestrian delay time for at least two 30-minute peak pedestrian delay periods of an average weekday or like periods of a Saturday or Sunday.
Queue length on stop-controlled approaches.

Section 4C.02 Warrant 1, Eight-Hour Vehicular Volume

Support:
The Minimum Vehicular Volume, Condition A, is intended for application where a large volume of intersecting traffic is the principal reason to consider installing a traffic control signal.

The Interruption of Continuous Traffic, Condition B, is intended for application where the traffic volume on a major street is so heavy that traffic on a minor intersecting street suffers excessive delay or conflict in entering or crossing the major street.

Standard:
The need for a traffic control signal shall be considered if an engineering study finds that one of the following conditions exist for each of any 8 hours of an average day:

The vehicles per hour given in both of the 100 percent columns of Condition A in Table 4C-1 exist on the major-street and the higher-volume minor-street approaches, respectively, to the intersection; or
The vehicles per hour given in both of the 100 percent columns of Condition B in Table 4C-1 exist on the major-street and the higher-volume minor-street approaches, respectively, to the intersection.

In applying each condition the major-street and minor-street volumes shall be for the same 8 hours. On the minor street, the higher volume shall not be required to be on the same approach during each of these 8 hours.

Option:
If the posted or statutory speed limit or the 85th-percentile speed on the major street exceeds 70 km/h (40 mph), or if the intersection lies within the built-up area of an isolated community having a population of less than 10,000, the traffic volumes in the 70 percent columns in Table 4C-1 may be used in place of the 100 percent columns.

Table 4C-1. Warrant 1, Eight-Hour Vehicular Volume

Condition A —Minimum Vehicular Volume
Number of lanes for moving traffic on each approach		Vehicles per hour on major street (total of both approaches)			Vehicles per hour on higher-volume minor-street approaches (one direction only)
Major Street	Minor Street	100%^a	80%^b	70%^c	100%^a	80%^b	70%^c
1	1	500	400	350	150	120	105
2 or more	1	600	480	420	150	120	105
2 or more	2 or more	600	480	420	200	160	140
1	2 or more	500	400	350	200	160	140

Condition B—Interruption of Continuous Traffic
Number of lanes for moving traffic on each approach		Vehicles per hour on major street (total of both approaches)			Vehicles per hour on higher-volume minor-street approaches (one direction only)
Major Street	Minor Street	100%^a	80%^b	70%^c	100%^a	80%^b	70%^c
1	1	750	600	525	75	60	53
2 or more	1	900	720	630	75	60	53
2 or more	2 or more	900	720	630	100	80	70
1	2 or more	750	600	525	100	80	70
^aBasic minimum hourly volume. ^bUsed for combination of Conditions A and B after adequate trial of other remedial measures. ^cMay be used when the major-street speed exceeds 70 km/h (40 mph) or in an isolated community with a population of less than 10,000.

Standard:
The need for a traffic control signal shall be considered if an engineering study finds that both of the following conditions exist for each of any 8 hours of an average day:

The vehicles per hour given in both of the 80 percent columns of Condition A in Table 4C-1 exist on the major-street and the higher-volume minor-street approaches, respectively, to the intersection; and
The vehicles per hour given in both of the 80 percent columns of Condition B in Table 4C-1 exist on the major-street and the higher-volume minor-street approaches, respectively, to the intersection.

These major-street and minor-street volumes shall be for the same 8 hours for each condition; however, the 8 hours satisfied in Condition A shall not be required to be the same 8 hours satisfied in Condition B. On the minor street, the higher volume shall not be required to be on the same approach during each of the 8 hours.

Guidance:
The combination of Conditions A and B should be applied only after an adequate trial of other alternatives that could cause less delay and inconvenience to traffic has failed to solve the traffic problems.

Return to Part 4 Table of Contents

Section 4C.03 Warrant 2, Four-Hour Vehicular Volume

Support:
The Four-Hour Vehicular Volume signal warrant conditions are intended to be applied where the volume of intersecting traffic is the principal reason to consider installing a traffic control signal.

Standard:
The need for a traffic control signal shall be considered if an engineering study finds that, for each of any 4 hours of an average day, the plotted points representing the vehicles per hour on the major street (total of both approaches) and the corresponding vehicles per hour on the higher-volume minor-street approach (one direction only) all fall above the applicable curve in Figure 4C-1 for the existing combination of approach lanes. On the minor street, the higher volume shall not be required to be on the same approach during each of these 4 hours.

Figure 4C-1 Warrant 2, Four-Hour Vehicular Volume [D]

Thumbnail image of Figure 4C-1

Option:
If the posted or statutory speed limit or the 85th-percentile speed on the major street exceeds 70 km/h (40 mph) or if the intersection lies within the built-up area of an isolated community having a population of less than 10,000, Figure 4C-2 may be used in place of Figure 4C-1.

Figure 4C-2. Warrant 2, Four-Hour Vehicular Volume (70% Factor) [D]

Thumbnail image of Figure 4C-2

Section 4C.04 Warrant 3, Peak Hour

Support:
The Peak Hour signal warrant is intended for use at a location where traffic conditions are such that for a minimum of 1 hour of an average day, the minor-street traffic suffers undue delay when entering or crossing the major street.

Standard:
This signal warrant shall be applied only in unusual cases. Such cases include, but are not limited to, office complexes, manufacturing plants, industrial complexes, or high-occupancy vehicle facilities that attract or discharge large numbers of vehicles over a short time.

The need for a traffic control signal shall be considered if an engineering study finds that the criteria in either of the following two categories are met:

If all three of the following conditions exist for the same 1 hour (any four consecutive 15-minute periods) of an average day:

The total stopped time delay experienced by the traffic on one minor-street approach (one direction only) controlled by a STOP sign equals or exceeds: 4 vehicle-hours for a one-lane approach; or 5 vehicle-hours for a two-lane approach, and
The volume on the same minor-street approach(one direction only) equals or exceeds 100 vehicles per hour for one moving lane of traffic or 150 vehicles per hour for two moving lanes, and
The total entering volume serviced during the hour equals or exceeds 650 vehicles per hour for intersections with three approaches or 800 vehicles per hour for intersections with four or more approaches.

The plotted point representing the vehicles per hour on the major street (total of both approaches) and the corresponding vehicles per hour on the higher-volume minor-street approach (one direction only) for 1 hour (any four consecutive 15-minute periods) of an average day falls above the applicable curve in Figure 4C-3 for the existing combination of approach lanes.

Figure 4C-3 Warrant 3, Peak Hour [D]

Option:
If the posted or statutory speed limit or the 85th-percentile speed on the major street exceeds 70 km/h (40 mph), or if the intersection lies within the built-up area of an isolated community having a population of less than 10,000, Figure 4C-4 may be used in place of Figure 4C-3 to satisfy the criteria in the second category of the Standard.

Figure 4C-4 Warrant 3, Peak Hour (70% Factor) [D]

Section 4C.05 Warrant 4, Pedestrian Volume

Support:
The Pedestrian Volume signal warrant is intended for application where the traffic volume on a major street is so heavy that pedestrians experience excessive delay in crossing the major street.

Standard:
The need for a traffic control signal at an intersection or midblock crossing shall be considered if an engineering study finds that both of the following criteria are met:

The pedestrian volume crossing the major street at an intersection or midblock location during an average day is 100 or more for each of any 4 hours or 190 or more during any 1 hour; and
There are fewer than 60 gaps per hour in the traffic stream of adequate length to allow pedestrians to cross during the same period when the pedestrian volume criterion is satisfied. Where there is a divided street having a median of sufficient width for pedestrians to wait, the requirement applies separately to each direction of vehicular traffic.

The Pedestrian Volume signal warrant shall not be applied at locations where the distance to the nearest traffic control signal along the major street is less than 90 m (300 ft), unless the proposed traffic control signal will not restrict the progressive movement of traffic.

If a traffic control signal is justified by both this signal warrant and a traffic engineering study, the traffic control signal shall be equipped with pedestrian signal heads conforming to requirements set forth in Chapter 4E.

Guidance:
If a traffic control signal is justified by both this signal warrant and a traffic engineering study:

If installed within a signal system, the traffic control signal should be coordinated.
At an intersection, the traffic control signal should be traffic-actuated and should include pedestrian detectors. As a minimum, it should have semiactuated operation, but full-actuated operation with detectors on all approaches might also be appropriate.
At nonintersection crossings, the traffic control signal should be pedestrian-actuated, parking and other sight obstructions should be prohibited for at least 30 m (100 ft) in advance of and at least 6.1 m (20 ft) beyond the crosswalk, and the installation should include suitable standard signs and pavement markings.

Option:
The criterion for the pedestrian volume crossing the major roadway may be reduced as much as 50 percent if the average crossing speed of pedestrians is less than 1.2 m/sec (4 ft/sec).

A traffic control signal may not be needed at the study location if adjacent coordinated traffic control signals consistently provide gaps of adequate length for pedestrians to cross the street, even if the rate of gap occurrence is less than one per minute.

Return to Part 4 Table of Contents

Section 4C.06 Warrant 5, School Crossing

Support:
The School Crossing signal warrant is intended for application where the fact that school children cross the major street is the principal reason to consider installing a traffic control signal.

Standard:
The need for a traffic control signal shall be considered when an engineering study of the frequency and adequacy of gaps in the vehicular traffic stream as related to the number and size of groups of school children at an established school crossing across the major street shows that the number of adequate gaps in the traffic stream during the period when the children are using the crossing is less than the number of minutes in the same period (see Section 7A.03) and there are a minimum of 20 students during the highest crossing hour.

Before a decision is made to install a traffic control signal, consideration shall be given to the implementation of other remedial measures, such as warning signs and flashers, school speed zones, school crossing guards, or a grade-separated crossing.

The School Crossing signal warrant shall not be applied at locations where the distance to the nearest traffic control signal along the major street is less than 90 m (300 ft), unless the proposed traffic control signal will not restrict the progressive movement of traffic.

Guidance:
If a traffic control signal is justified by both this signal warrant and an engineering study:

If installed within a signal system, the traffic control signal should be coordinated.
At an intersection, the traffic control signal should be traffic-actuated and should include pedestrian detectors. As a minimum, it should have semiactuated operation, but full-actuated operation with detectors on all approaches might also be appropriate.
At nonintersection crossings, the traffic control signal should be pedestrian-actuated, parking and other sight obstructions should be prohibited for at least 30 m (100 ft) in advance of and at least 6.1 m (20 ft) beyond the crosswalk, and the installation should include suitable standard signs and pavement markings.

Section 4C.07 Warrant 6, Coordinated Signal System

Support:
Progressive movement in a coordinated signal system sometimes necessitates installing traffic control signals at intersections where they would not otherwise be needed in order to maintain proper platooning of vehicles.

Standard:
The need for a traffic control signal shall be considered if an engineering study finds that one of the following criteria is met:

On a one-way street or a street that has traffic predominantly in one direction, the adjacent traffic control signals are so far apart that they do not provide the necessary degree of vehicular platooning.
On a two-way street, adjacent traffic control signals do not provide the necessary degree of platooning and the proposed and adjacent traffic control signals will collectively provide a progressive operation.

Guidance:
The Coordinated Signal System signal warrant should not be applied where the resultant spacing of traffic control signals would be less than 300 m (1,000 ft).

Section 4C.08 Warrant 7, Crash Experience

Support:
The Crash Experience signal warrant conditions are intended for application where the severity and frequency of crashes are the principal reasons to consider installing a traffic control signal.

Standard:
The need for a traffic control signal shall be considered if an engineering study finds that all of the following criteria are met:

Adequate trial of alternatives with satisfactory observance and enforcement has failed to reduce the crash frequency; and
Five or more reported crashes, of types susceptible to correction by a traffic control signal, have occurred within a 12-month period, each crash involving personal injury or property damage apparently exceeding the applicable requirements for a reportable crash; and
For each of any 8 hours of an average day, the vehicles per hour (vph) given in both of the 80 percent columns of Condition A in Table 4C-1 (see Section 4C.02), or the vph in both of the 80 percent columns of Condition B in Table 4C-1 exists on the major-street and the higher-volume minor-street approach, respectively, to the intersection, or the volume of pedestrian traffic is not less than 80 percent of the requirements specified in the Pedestrian Volume warrant. These major-street and minor-street volumes shall be for the same 8 hours. On the minor street, the higher volume shall not be required to be on the same approach during each of the 8 hours.

Section 4C.09 Warrant 8, Roadway Network

Support:
Installing a traffic control signal at some intersections might be justified to encourage concentration and organization of traffic flow on a roadway network.

Standard:
The need for a traffic control signal shall be considered if an engineering study finds that the common intersection of two or more major routes meets one or both of the following criteria:

The intersection has a total existing, or immediately projected, entering volume of at least 1,000 vehicles per hour during the peak hour of a typical weekday and has 5-year projected traffic volumes, based on an engineering study, that meet one or more of Warrants 1, 2, and 3 during an average weekday; or
The intersection has a total existing or immediately projected entering volume of at least 1,000 vehicles per hour for each of any 5 hours of a nonnormal business day (Saturday or Sunday).

A major route as used in this signal warrant shall have one or more of the following characteristics:

It is part of the street or highway system that serves as the principal roadway network for through traffic flow; or
It includes rural or suburban highways outside, entering, or traversing a city; or
It appears as a major route on an official plan, such as a major street plan in an urban area traffic and transportation study.

Return to Part 4 Table of Contents

CHAPTER 4D. TRAFFIC CONTROL SIGNAL FEATURES

Section 4D.01 General

Support:
The features of traffic control signals of interest to road users are the location, design, and meaning of the signal indications. Uniformity in the design features that affect the traffic to be controlled, as set forth in this Manual, is especially important for safe and efficient traffic operations.

Pavement markings (see Part 3) that clearly communicate the operational plan of an intersection to road users play an important role in the effective operation of traffic control signals. By designating the number of lanes, the use of each lane, the length of additional lanes on the approach to an intersection, and the proper stopping points, the engineer can design the signal phasing and timing to best match the goals of the operational plan.

Standard:
A traffic control signal shall be operated in either a steady (stop-and-go) mode or a flashing mode at all times.

A traffic control signal shall control traffic only at the intersection or midblock location where the signal faces are placed.

STOP signs shall not be used in conjunction with any traffic control signal operation, except in either of the following cases:

If the signal indication for an approach is a flashing red at all times; or
If a minor street or driveway is located within or adjacent to the area controlled by the traffic control signal, but does not require separate traffic signal control because an extremely low potential for conflict exists.

When a traffic control signal is not in operation, such as before it is placed in service, during seasonal shutdowns, or when it is not desirable to operate the traffic control signal, the signal faces shall be covered, turned, or taken down to clearly indicate that the traffic control signal is not in operation.

Guidance:
Pavement markings should be used at traffic control signal locations as provided in Part 3. If the road surface will not retain pavement markings, signs should be installed to provide the needed road user information.

Engineering judgment should be used to determine the proper phasing and timing for a traffic control signal. Since traffic flows and patterns change, phasing and timing should be reevaluated regularly and updated if needed.

Section 4D.02 Responsibility for Operation and Maintenance

Guidance:
Prior to installing any traffic control signal, the responsibility for the maintenance of the signal and all of the appurtenances, hardware, software, and the timing plan(s) should be clearly established. The responsible agency should provide for the maintenance of the traffic control signal and all of its appurtenances in a competent manner.

To this end the agency should:

Keep every controller assembly in effective operation in accordance with its predetermined timing schedule; check the operation of the controller assembly frequently enough to ensure that it is operating in accordance with the predetermined timing schedule; and ensure that a record of all timing changes is maintained and that only authorized persons make timing changes;
Clean the optical system of the signal sections and replace the light sources as frequently as experience proves necessary;
Clean and service equipment and other appurtenances as frequently as experience proves necessary;
Provide for alternate operation of the traffic control signal during a period of failure, using flashing mode or manual control, or manual traffic direction by proper authorities as might be required by traffic volumes or congestion, or by erecting other traffic control devices;
Have properly skilled maintenance personnel available without undue delay for all emergency and lamp failure calls;
Provide spare equipment to minimize the interruption of traffic control signal operation as a result of equipment failure;
Provide for the availability of properly skilled maintenance personnel for the repair of all components; and
Maintain the appearance of the signal displays and equipment.

Section 4D.03 Provisions for Pedestrians

Support:
Chapter 4E contains additional information regarding pedestrian signals.

Standard:
The design and operation of traffic control signals shall take into consideration the needs of pedestrian as well as vehicular traffic.

If engineering judgment indicates the need for provisions for a given pedestrian movement, signal faces conveniently visible to pedestrians shall be provided by pedestrian signal heads or a signal face for an adjacent vehicular movement.

Guidance:

Safety considerations should include the installation, where appropriate, of accessible pedestrian signals (see Sections 4E.06 and 4E.08) that provide information in nonvisual format (such as audible tones, verbal messages, and/or vibrating surfaces).

Where pedestrian movements regularly occur, pedestrians should be provided with sufficient time to cross the roadway by adjusting the traffic control signal operation and timing to provide sufficient crossing time every cycle or by providing pedestrian detectors.

Option:
If it is desirable to prohibit certain pedestrian movements at a traffic control signal, a PEDESTRIANS PROHIBITED (R9-3) or No Pedestrian Crossing (R9-3a) sign may be used (see Section 2B.39).

Section 4D.04 Meaning of Vehicular Signal Indications

Support:
The "Uniform Vehicle Code" (see Section 1A.11) is the primary source for the standards for the meaning of vehicular signal indications to both vehicle operators and pedestrians as set forth below, and the standards for the meaning of separate pedestrian signal indications as set forth in Section 4E.02.

Standard:
Unless otherwise determined by law, the following meanings shall be given to highway traffic signal indications for vehicles and pedestrians:

Steady green signal indications shall have the following meanings:
1. Traffic, except pedestrians, facing a CIRCULAR GREEN signal indication may proceed straight through or turn right or left except as such movement is modified by lane-use signs, turn prohibition signs, lane markings, or roadway design. But vehicular traffic, including vehicles turning right or left, shall yield the right-of-way to other vehicles, and to pedestrians lawfully within the intersection or an adjacent crosswalk, at the time such signal indication is exhibited.
2. Traffic, except pedestrians, facing a GREEN ARROW signal indication, shown alone or in combination with another signal indication, may cautiously enter the intersection only to make the movement indicated by such arrow, or such other movement as is permitted by other signal indications shown at the same time. Such vehicular traffic shall yield the right-of-way to pedestrians lawfully within an adjacent crosswalk and to other traffic lawfully using the intersection.
3. Unless otherwise directed by a pedestrian signal head, pedestrians facing any green signal indication, except when the signal indication is a turn arrow for a vehicular movement in conflict with the desired path of the pedestrian, may proceed across the roadway within any marked or unmarked crosswalk.
Steady yellow signal indications shall have the following meanings:
1. Traffic, except pedestrians, facing a steady CIRCULAR YELLOW or YELLOW ARROW signal indication is thereby warned that the related green movement is being terminated or that a red signal indication will be exhibited immediately thereafter when vehicular traffic shall not enter the intersection.
2. Pedestrians facing a steady CIRCULAR YELLOW or YELLOW ARROW signal indication, unless otherwise directed by a pedestrian signal head, are thereby advised that there is insufficient time to cross the roadway before a red signal indication is shown, and no pedestrian shall then start to cross the roadway.
Steady red signal indications shall have the following meanings:

Vehicular traffic facing a steady CIRCULAR RED signal indication alone shall stop at a clearly marked stop line, but if there is no stop line, traffic shall stop before entering the crosswalk on the near side of the intersection; or if there is no crosswalk, then before entering the intersection, and shall remain stopped until a signal indication to proceed is shown, or as provided below.

Except when a sign is in place prohibiting a turn on red or a RED ARROW signal indication is displayed, vehicular traffic facing a CIRCULAR RED signal indication may enter the intersection to turn right, or to turn left from a one-way street into a one-way street, after stopping. Such vehicular traffic shall yield the right-of-way to pedestrians lawfully within an adjacent crosswalk and to other traffic lawfully using the intersection.

Vehicular traffic facing a steady RED ARROW signal indication shall not enter the intersection to make the movement indicated by the arrow (except as described in the Option below) and, unless entering the intersection to make another movement permitted by another signal indication, shall stop at a clearly marked stop line; but if there is no stop line, before entering the crosswalk on the near side of the intersection, or if there is no crosswalk, then before entering the intersection, and shall remain stopped until a signal indication permitting the movement indicated by such RED ARROW is shown.
Unless otherwise directed by a pedestrian signal head, pedestrians facing a steady CIRCULAR RED or RED ARROW signal indication alone shall not enter the roadway.

Flashing signal indications shall have the following meanings:

Flashing yellow—When a yellow lens is illuminated with rapid intermittent flashes, vehicular traffic may proceed through the intersection or past such signal indication only with caution.
Flashing red—When a red lens is illuminated with rapid intermittent flashes, vehicular traffic shall stop at a clearly-marked stop line; but if there is no stop line, traffic shall stop before entering the crosswalk on the near side of the intersection; or if there is no crosswalk, at the point nearest the intersecting roadway where the driver has a view of approaching traffic on the intersecting roadway before entering the intersection. The right to proceed shall be subject to the rules applicable after making a stop at a STOP sign.
Flashing RED ARROW and flashing YELLOW ARROW signal indications have the same meaning as the corresponding flashing circular signal indication, except that they apply only to vehicular traffic intending to make the movement indicated by the arrow.

Option:
Where turns are allowed on red and the signal indication is an arrow, a sign may be used to indicate that turns are allowed on red after stopping.

Return to Part 4 Table of Contents

Section 4D.05 Application of Steady Signal Indications

Standard:
When a traffic control signal is being operated in a steady (stop-and-go) mode, at least one lens in each signal face shall be illuminated at any given time.

A signal face(s) that controls a particular vehicular movement during any interval of a cycle shall control that same movement during all intervals of the cycle.

Steady signal indications shall be applied as follows:

A steady CIRCULAR RED signal indication:

Shall be displayed when it is intended to prohibit traffic, except pedestrians directed by a pedestrian signal head, from entering the intersection or other controlled area. Turning after stopping is permitted as stated in Section 4D.04(C)(1).
Shall be displayed with the appropriate GREEN ARROW signal indications when it is intended to permit traffic to make a specified turn or turns, and to prohibit traffic from proceeding straight ahead through the intersection or other controlled area, except in protected only mode turn signal faces.

A steady CIRCULAR YELLOW signal indication:

Shall be displayed following a CIRCULAR GREEN or straight-through GREEN ARROW signal indication in the same signal face.
Shall not be displayed in conjunction with the change from the CIRCULAR RED signal indication to the CIRCULAR GREEN signal indication.
Shall be followed by a CIRCULAR RED signal indication except that, when entering preemption operation, the return to the previous CIRCULAR GREEN signal indication shall be permitted following a CIRCULAR YELLOW signal indication (see Section 4D.13).

A steady CIRCULAR GREEN signal indication shall be displayed only when it is intended to permit traffic to proceed in any direction that is lawful and practical.
A steady RED ARROW signal indication shall be displayed when it is intended to prohibit traffic, except pedestrians directed by a pedestrian signal head, from entering the intersection or other controlled area to make the indicated turn. Turning on a steady RED ARROW signal indication shall not be permitted.
A steady YELLOW ARROW signal indication:

Shall be displayed in the same direction as a GREEN ARROW signal indication following a GREEN ARROW signal indication in the same signal face, unless:

The GREEN ARROW signal indication and a CIRCULAR GREEN (or straight-through GREEN ARROW) signal indication terminate simultaneously in the same signal face, or
The green arrow is a straight-through GREEN ARROW.

Shall not be displayed in conjunction with the change from a RED ARROW signal indication to a GREEN ARROW signal indication.
Shall not be displayed when any conflicting vehicular movement has a green or yellow signal indication or any conflicting pedestrian movement has a WALKING PERSON (symbolizing WALK) or flashing UPRAISED HAND (symbolizing DONT WALK) signal indication (see Section 4D.09).
Shall be terminated by a RED ARROW signal indication for the same direction or a CIRCULAR RED signal indication except:

When entering preemption operation, the return to the previous GREEN ARROW signal indication shall be permitted following a YELLOW ARROW signal indication.
When the movement controlled by the arrow is to continue on a permissive mode basis during an immediately following CIRCULAR GREEN signal indication.

A steady GREEN ARROW signal indication:

Shall be displayed only to allow vehicular movements, in the direction indicated, that are not in conflict with other vehicles moving on a green or yellow signal indication or with pedestrians crossing in conformance with a WALKING PERSON (symbolizing WALK) or flashing UPRAISED HAND (symbolizing DONT WALK) signal indication (see Section 4D.09).
Shall be displayed on a signal face that controls a left-turn movement when said movement is not in conflict with other vehicles moving on a green or yellow signal indication or with pedestrians crossing in conformance with a WALKING PERSON (symbolizing WALK) or flashing UPRAISED HAND (symbolizing DONT WALK) signal indication (see Section 4D.09).
Shall not be required on the stem of T-intersections or for turns from one-way streets.

Option:
Steady RED ARROW, YELLOW ARROW, and GREEN ARROW signal indications, if not otherwise prohibited, may be used instead of the corresponding circular signal indications at the following locations:

On an approach intersecting a one-way street;
Where certain movements are prohibited; and
Where certain movements are physically impossible.

Section 4D.06 Application of Steady Signal Indications for Left Turns

Support:
Left-turning traffic is controlled by one of four modes as follows:

Permissive Only Mode—turns made on the CIRCULAR GREEN signal indication after yielding to oncoming traffic and pedestrians;
Protected Only Mode—turns made only when the left-turn GREEN ARROW signal indication is displayed;
Protected/Permissive Mode—both modes occur on an approach during the same cycle; or
Variable Left-Turn Mode—the operating mode changes among the protected only mode and/or the protected/permissive mode and/or the permissive only mode during different periods of the day.

Option:
In areas having a high percentage of elderly drivers, special consideration may be given to the use of protected only mode left-turn phasing, when appropriate.

Standard:
The required left-turn signal faces and operation for an approach shall be determined by the selected mode of left-turn operation, as follows:

Permissive Only Mode—The signal indication for permissive only mode left turns shall be the same color as the signal indication for through traffic. A separate signal indication or signal face for left turns shall not be required.
Protected Only Mode—The left-turn signal face shall be capable of displaying one of the following sets of signal indications:

Left-turn RED ARROW, YELLOW ARROW, and GREEN ARROW signal indications only. At least one left-turn signal face shall be provided in addition to the two approach signal faces required in Section 4D.15 for the through movement. Only one of the three colors shall be illuminated at any given time. A signal instruction sign shall not be required with this set of signal indications. If used, it shall be a LEFT ON GREEN ARROW ONLY sign (R10-5); or
CIRCULAR RED, left-turn YELLOW ARROW, and left-turn GREEN ARROW signal indications. At least one left-turn signal face shall be provided in addition to the two approach signal faces required in Section 4D.15 for the through movement. Only one of the three colors shall be illuminated at any given time. Unless the CIRCULAR RED signal indication is shielded, hooded, louvered, positioned, or designed such that it cannot be seen by drivers in the through lane(s), either a LEFT TURN SIGNAL sign (R10-10) or a visibility-limited CIRCULAR RED signal indication shall be used.
CIRCULAR RED, CIRCULAR YELLOW, CIRCULAR GREEN, and left-turn GREEN ARROW signal indications. This four-section signal face shall be used only when the CIRCULAR GREEN and left-turn GREEN ARROW signal indications begin and terminate together. During each interval, the circular signal indication shall be the same color as the signal indication on the signal face(s) for the adjacent through traffic.

Protected/Permissive Mode—The signal indications for protected/permissive mode left turns shall be provided either in a shared signal face (to be shared by left-turning and through traffic) or in a separate signal face intended to be exclusively used by left-turning traffic.
If a shared signal face is provided, it shall be considered an approach signal face, and shall meet the following requirements:

During the protected left-turn movement, the signal face shall simultaneously display:

A left-turn GREEN ARROW signal indication, and
A circular signal indication that is the same color as the signal indication for the adjacent through lane on the same approach as the protected left turn.

During the protected left-turn movement, the signal faces for through traffic on the opposing approach shall simultaneously display CIRCULAR RED signal indications.

During the permissive left-turn movement, all signal faces on the approach shall display CIRCULAR GREEN signal indications.
All signal faces on the approach shall simultaneously display the same color of circular signal indications to both through and left-turn road users.
A supplementary sign shall not be required. If used, it shall be a LEFT TURN YIELD ON GREEN (symbolic green ball) sign (R10-12).

If a separate signal face is provided, it shall be considered a left-turn signal face, and shall meet the following requirements:

During the protected left-turn movement, the left-turn signal face shall simultaneously display:

A left-turn GREEN ARROW signal indication, and
A CIRCULAR RED signal indication.

During the protected left-turn movement, the signal faces for through traffic on the opposing approach shall simultaneously display CIRCULAR RED signal indications.

During the permissive left-turn movement, the left-turn signal face shall display a CIRCULAR GREEN signal indication.
If the CIRCULAR GREEN and CIRCULAR YELLOW signal indications in the left-turn signal face are visibility-limited from the adjacent through movement, the left-turn signal face shall not be required to simultaneously display the same color of circular signal indication as the signal faces for the adjacent through movement.
If the CIRCULAR GREEN and CIRCULAR YELLOW signal indications in the left-turn signal face are visibility-limited from the adjacent through movement, the display of a CIRCULAR GREEN signal indication for a permissive left-turn movement while the signal faces for the adjacent through movement display CIRCULAR RED signal indications and the opposing left-turn signal face displays a left-turn GREEN ARROW for a protected left-turn movement shall be permitted.
If the left-turn signal face d signal indication as the signal faces for the adjacent through movement,oes not simultaneously display the same color of circular a combination of a LEFT TURN SIGNAL sign (R10-11) and a LEFT TURN YIELD ON GREEN (symbolic green ball) sign (R10-12) sign shall be used.

Variable Left-Turn Mode—If the protected only mode occurs during one or more periods of the day, and the permissive only mode or the combined protected/permissive mode occurs during other periods of the day, the requirements of Paragraphs A, B, and C above that are appropriate to that mode of operation shall be met, subject to the following:

The CIRCULAR GREEN and CIRCULAR YELLOW signal indications shall not be displayed when operating in the protected only mode.
The left-turn GREEN ARROW and left-turn YELLOW ARROW signal indications shall not be displayed when operating in the permissive only mode.

Option:
Additional appropriate signal indications or changeable message signs may be used to meet the requirements for the variable left-turn mode.

Return to Part 4 Table of Contents

Section 4D.07 Application of Steady Signal Indications for Right Turns

Support:
Right-turning traffic is controlled by one of four modes as follows:

Permissive Only Mode—turns made on the CIRCULAR GREEN signal indication after yielding to pedestrians.
Protected Only Mode—turns made only when the right-turn GREEN ARROW signal indication is displayed.
Protected/Permissive Mode—both modes occur on an approach during the same cycle.
Variable Right-Turn Mode—the operating mode changes among the protected only mode and/or the protected/permissive mode and/or the permissive only mode during different periods of the day.

Standard:
The required right-turn signal faces and operation for an approach shall be determined by the selected mode of right-turn operation, as follows:

Permissive Only Mode—A separate signal indication or signal face for right turns shall not be required. The signal indication for permissive only mode right turns shall be the same color as the signal indication for adjacent through traffic, except that if the right turn is held to provide an exclusive pedestrian movement, a separate right-turn RED ARROW signal indication shall be provided.
Protected Only Mode—The right-turn signal face shall be capable of displaying one of the following sets of signal indications:

Right-turn RED ARROW, YELLOW ARROW, and GREEN ARROW signal indications only. At least one right-turn signal face shall be provided in addition to the two approach signal faces required in Section 4D.15 for the through movement. Only one of the three colors shall be illuminated at any given time. A signal instruction sign shall not be required with this set of signal indications. If used, it shall be a RIGHT ON GREEN ARROW ONLY sign(R10-5a); or
CIRCULAR RED, right-turn YELLOW ARROW, and right-turn GREEN ARROW signal indications. At least one right-turn signal face shall be provided in addition to the two approach signal faces required in Section 4D.15 for the through movement. Only one of three colors shall be illuminated at any given time. Unless the CIRCULAR RED signal indication is shielded, hooded, louvered, positioned, or designed such that it cannot be seen by drivers in the through lane(s), either a RIGHT TURN SIGNAL sign (R10-10) or a visibility-limited CIRCULAR RED signal indication shall be used.
CIRCULAR RED, CIRCULAR YELLOW, CIRCULAR GREEN, and right-turn GREEN ARROW signal indications. This four-section signal face shall be used only when the CIRCULAR GREEN and right-turn GREEN ARROW signal indications begin and terminate together. During each interval, the circular signal indication shall be the same color as the signal indication on the signal faces for the adjacent through traffic.

Protected/Permissive Mode—A separate signal face is not required for the right turn, but, if provided, it shall be considered an approach signal face, and shall meet the following requirements:

During the protected right-turn movement, the signal face shall simultaneously display:

A right-turn GREEN ARROW signal indication, and
A circular signal indication that is the same color as the signal indication for the adjacent through lane on the same approach as the protected right turn.

During the permissive right-turn movement, all signal faces on the approach shall display a CIRCULAR GREEN signal indication.
All signal faces on the approach shall simultaneously display the same color of circular signal indications to both through and right-turn road users.

Variable Right-Turn Mode—If the protected only mode occurs during one or more periods of the day, and the permissive only mode or the combined protected/permissive mode occurs during other periods of the day, the requirements of Paragraphs A, B, and C above that are appropriate to that mode of operation shall be met subject to the following:
1. The CIRCULAR GREEN and CIRCULAR YELLOW signal indications shall not be displayed when operating in the protected only mode.
2. The right-turn GREEN ARROW and right-turn YELLOW ARROW signal indications shall not be displayed when operating in the permissive only mode.

Option:
Additional appropriate signal indications or changeable message signs may be used to meet the requirements for the variable right-turn mode.

Return to Part 4 Table of Contents

Section 4D.08 Prohibited Steady Signal Indications

Standard:
The following combinations of signal indications shall not be simultaneously displayed on any one signal face:

CIRCULAR GREEN with CIRCULAR YELLOW.
CIRCULAR RED with CIRCULAR YELLOW.
CIRCULAR GREEN with CIRCULAR RED.
Straight-through GREEN ARROW with CIRCULAR RED.

The above combinations shall not be simultaneously displayed in different signal faces on any one approach unless one of the following conditions exists:

One of the signal faces is a turn signal controlling a protected only mode turn, and a LEFT (RIGHT) TURN SIGNAL sign (R10-10) (see Sections 4D.06 and 4D.07) is mounted adjacent to each such signal face, or
The signal faces are shielded, hooded, louvered, positioned, or designed so that the combination is not confusing to approaching road users.

A straight-through RED ARROW signal indication or a straight-through YELLOW ARROW signal indication shall not be displayed on any signal face, either alone or in combination with any other signal indication.

4D.09 Unexpected Conflicts During Green or Yellow Intervals

Standard:
A steady GREEN ARROW or YELLOW ARROW signal indication shall not be displayed to vehicular movements that are in conflict with the following:

Other vehicles moving on a green or yellow signal indication. Vehicles departing in the same direction shall not be considered in conflict if, for each turn lane with moving traffic, there is a separate departing lane, and pavement markings or raised channelization clearly indicate which departure lane to use.
Pedestrians crossing in conformance with a WALKING PERSON (symbolizing WALK) or flashing UPRAISED HAND (symbolizing DONT WALK) signal indication.

Guidance:
No movement that creates an unexpected crossing of pathways of moving vehicles or pedestrians should be allowed during any green or yellow interval, except when all three of the following conditions are met:

The movement involves only slight conflict, and
Serious traffic delays are substantially reduced by permitting the conflicting movement, and
Drivers and pedestrians subjected to the unexpected conflict are effectively warned thereof by a sign.

Section 4D.10 Yellow Change and Red Clearance Intervals

Standard:
A yellow signal indication shall be displayed following every CIRCULAR GREEN or GREEN ARROW si