# Manual on Uniform Traffic Control Devices for Streets and Highways, 11th Edition/Part 2/Chapter 2A

Washington, DC: Federal Highway Administration, pages 39–64
PART 2 SIGNS
CHAPTER 2A. GENERAL
Section 2A.01 Function and Purpose of Signs
Support:
[01] This Manual contains Standards, Guidance, and Options for the signing of all types of highways, and site roadways open to public travel. The functions of signs are to provide regulations, warnings, and guidance information for road users. Words, symbols, and arrows are used to convey the messages. Signs are not typically used to confirm rules of the road (see Paragraph 4 of this Section).
[02] Detailed sign requirements are located in the following Chapters of Part 2:
    Chapter 2B—Regulatory Signs, Barricades, and Gates
    Chapter 2C—Warning Signs and Object Markers
    Chapter 2D—Guide Signs for Conventional Roads
    Chapter 2E—Guide Signs for Freeways and Expressways
    Chapter 2F—Toll Road Signs
    Chapter 2G—Preferential and Managed Lane Signs
    Chapter 2H—General Information Signs
    Chapter 2I—General Service Signs
    Chapter 2J—Specific Service Signs
    Chapter 2K—Tourist-Oriented Directional Signs
    Chapter 2L—Changeable Message Signs
    Chapter 2M—Recreational and Cultural Interest Area Signs
    Chapter 2N—Emergency Management Signs
[03] Definitions and acronyms that are applicable to signs are provided in Chapter 1C.
Guidance:
[04] Permanent signs should not be used on a frequent basis to confirm rules of the road or statutes. Instead, when determined necessary to advise of new regulations as part of an educational campaign, temporary signs or messages should be used instead of permanent signs. These temporary signs or messages should be used sparingly and only at strategic locations, and should be considered only as a supporting element of a larger educational campaign rather than as the primary source of notification. If engineering judgment determines a need for a permanent sign to distinguish between differing requirements of similar statutes in different jurisdictions, then a sign should be located in the vicinity of the jurisdictional boundary, and should be located away from warning, directional, and higher-priority regulatory signs, so as not to contribute to sign clutter (see Section 2A.20).
Section 2A.02 Standardization of Application
Support:
[01] It is recognized that urban traffic conditions differ from those in rural environments, and in many instances signs are applied and located differently. Where pertinent and practical, this Manual sets forth separate recommendations for urban and rural conditions.
[02] Low-volume rural roads typically include access to rural residences, agricultural, recreational, resource management and development (such as mining, logging, and grazing), and local roads in rural areas. On low-volume rural roads, the use of traffic control devices is limited to essential information regarding regulation, warning, and guidance. On low-volume rural roads, it is important to consider the needs of unfamiliar road users for occasional, recreational, and commercial transportation purposes.
Guidance:
[03] Signs should be used only where justified by engineering judgment or studies, as provided in Section 1D.03.
[04] Results from traffic engineering studies of physical and traffic safety or operational factors should indicate the locations where signs are deemed necessary or desirable.
Standard:
[06] Each standard sign (see Paragraph 1 of Section 2A.04) shall be displayed only for the specific purpose as prescribed in this Manual. Before any new highway, site roadway open to public travel (see definition in Section 1C.02), detour, or temporary route is opened to public travel, all necessary signs shall be in place. Signs required by road conditions or restrictions shall be removed when those conditions cease to exist or the restrictions are withdrawn.
Section 2A.03 Classification of Signs
Standard:
[01] Signs shall be defined by their function as follows:
* Regulatory signs give notice of traffic laws or regulations.
* Warning signs give notice of a situation that might not be readily apparent.
* Guide signs show route designations, destinations, directions, distances, services, points of interest, and other geographical, recreational, or cultural information.
Support:
[02] Barricades are described in Sections 2B.75 and 6K.07.
[03] Gates are described in Section 2B.76.
[04] Object markers are described in Section 2C.70.
Section 2A.04 Design of Signs
Support:
[01] This Manual shows many standard signs and object markers approved for use on streets, highways, bikeways, and pedestrian crossings. Standard signs and object markers have a standardized design, shape, background, and legend as shown in this Manual.
[02] In the provisions for individual standard signs and object markers, the general appearance of the legend, color, and size are shown in the accompanying tables and illustrations, and are not always detailed in the text.
[03] Detailed drawings of standard signs, object markers, alphabets, symbols, and arrows (see Figure 2D-3) are contained in the “Standard Highway Signs” publication. Section 1A.05 contains information regarding this publication.
[04] The basic requirements of a sign are that it be legible to those for whom it is intended and that it be understandable in time to allow for a proper response. Desirable attributes include:
* High visibility by day and night; and
* High legibility (adequately-sized letters, symbols, or arrows, and a short legend for quick comprehension by a road user approaching a sign).
[05] Standardized colors and shapes are specified so that the several classes of traffic signs can be promptly recognized. Simplicity and uniformity in design, position, and application are essential for a sign to be effective.
Standard:
[06] The term legend shall include all word messages and symbol and arrow designs that are intended to convey specific meanings.
[07] Uniformity in design shall include shape, color, dimensions, legends, letter style, borders, and illumination or retroreflectivity.
[08] Standardization of these designs does not preclude further improvement by minor modifications to the orientation of symbols (see Section 2A.09), width of borders, or layout of word messages, but all shapes and colors shall be as indicated.
[09] All symbols (see Section 2A.09) shall be unmistakably similar to, or mirror images of, the adopted symbol signs, all of which are shown in the “Standard Highway Signs” publication (see Section 1A.05). Symbols and colors shall not be modified unless otherwise provided in this Manual. All symbols, colors, or other design features for signs not shown in the “Standard Highway Signs” publication (see Section 1A.05) shall follow the procedures for experimentation and change described in Chapter 1B.
[10] Where a standard word message is applicable, the wording shall be as provided in this Manual.
[11] In situations where word messages are necessary other than those provided in this Manual (see Paragraph 15 of this Section), the signs shall be of the same shape and color as standard signs of the same functional type.
[13] Where a standard sign provided in this Manual or the “Standard Highway Signs” publication (see Section 1A.05) is applicable, an alternative legend sign or alternative sign design shall not be allowed in place of the standardized legend or design except as provided in this Manual.
[14] Where a standard sign provided in this Manual or the “Standard Highway Signs” publication (see Section 1A.05) is applicable, but the legend is variable, such as for destination names, an alternative sign design or dimensions shall not be allowed in place of the standardized design for the non-variable elements except as provided in this Manual.
Option:
[15] State and local highway agencies and owners of site roadways open to public travel may develop special word legend signs in situations where engineering judgment determines roadway conditions make it necessary to provide road users with additional regulatory, warning, or guidance information, such as when road users need to be notified of special regulations or warned about a situation that might not be readily apparent. Unlike colors that have not been assigned or symbols that have not been approved for signs, new word legend signs may be used without the need for experimentation.
Support:
[16] The message conveyed by some special word legend signs might be unclear to the road user. Although experimentation is not required for such word legends, they might still warrant an evaluation to determine comprehension or possible misinterpretation of the intended message by the road user.
[17] Scanning graphics are graphics designed for scanning by machine, and include bar codes, quick-response (QR) codes or other matrix bar-code formats, or similar graphics.
Standard:
[18] Unless otherwise provided in this Manual for a specific sign or as provided in Paragraph 19 of this Section, telephone numbers, Internet addresses, e-mail addresses, domain names, uniform resource locators (URL), metadata tags (“hash-tags”), and scanning graphics (see Paragraph 17 of this Section) for the purpose of obtaining information (other than those for maintenance or inventory purposes per the provisions of Paragraphs 21 through 23 of this Section) shall not be displayed on any sign, plaque, sign panel, or changeable message sign.
Option:
[19] Internet addresses, e-mail addresses, telephone numbers, scanning graphics, or other graphics for the purpose of conveying information may be displayed on the face of signs, plaques, sign panels, and changeable message signs that are oriented away from or otherwise not readily visible to operators of motor vehicles but rather are intended for viewing only by pedestrians, occupants of parked vehicles, and driving automation systems.
Standard:
[20] Pictographs (see definition in Section 1C.02) shall not be displayed on signs except as specifically provided in this Manual for a particular type of sign. Pictographs shall be simple, dignified, and devoid of any advertising and shall not contain any scanning graphics (see Paragraph 17 of this Section) for the purpose of conveying information. When used to represent a political jurisdiction (a State, county, or municipal corporation) the pictograph shall be the official designation adopted by the jurisdiction, except as provided otherwise in this Manual. When used to represent any other type of jurisdiction, the pictograph shall be the official designation adopted by the jurisdiction. When used to represent a college or university, the pictograph shall be the official seal adopted by the institution. College or university pictographs shall not include pictorial representations of university or college programs, or athletic mascots.
[21] No items other than official traffic control signs, inventory stickers or decals, sign installation dates, manufacturer name, sign sizes, sign designations, anti-vandalism stickers, inventory or maintenance codes, and maintenance-related scanning graphics shall be mounted on the back of a sign.
Option:
[22] The date of fabrication, sign designation, sign size, and/or manufacturer name may be displayed on the front of a sign face in accordance with the provisions of Paragraph 23 of this Section.
Standard:
Table 2A-1. Use of Sign Shapes :
| Shape | Signs |
| Octagon* | Stop (R1-1)** |
| Equilateral Triangle (downward-pointing)* | Yield (R1-2)** |
| Circle* | Grade Crossing Advance Warning (W10-1)** |
| Pennant (Isosceles Triangle with longer axis horizontal, pointed right)* | No Passing Zone (W14-3)** |
| Pentagon (upward-pointing)* | School (S1-1) (squared bottom corners)** County Route (M1-6) (tapered lower sides)** |
| Crossbuck (two rectangles in a perpendicular “X” configuration)* | Grade Crossing (R15-1)** |
| Diamond | Warning Series |
| Rectangle (including square) | Regulatory Series Guide Series*** Warning Series |
| Trapezoid* | Recreational and Cultural Interest Area Guide Series (isosceles or right-angled) National Forest Route Sign (M1-1) (isosceles)** |
* This shape shall be limited exclusively to the sign(s) indicated.
** This sign shall be exclusively the shape shown.
*** Guide series includes general service, specific service, tourist-oriented directional,
general information, recreational and cultural interest area, and emergency management signs.
Note: Signs with standardized designs shall not be modified to accommodate a different
shape except as provided in this Manual. :
Section 2A.05 Shapes
Standard:
[01] Particular shapes, as shown in Table 2A-1, shall be used exclusively for specific signs or series of signs, unless otherwise provided in this Manual for a particular sign or class of signs.
[02] The Crossbuck is a shape exclusive to the Grade Crossing (R15-1) sign and shall not be obscured by mounting a different shape sign on the back of the Crossbuck (see Section 8B.03).
Guidance:
[03] Shapes that are exclusive to a particular sign (such as an octagon for STOP, a pennant for NO PASSING ZONE, or a circle for Railroad Advance) should not be obscured by another sign mounted on the back of the same assembly protruding or extending beyond the edge of the sign with the exclusive shape. The following methods should be considered in lieu of mounting a sign on the back of another sign that would obscure the exclusive shape of the sign:
* Install the signs on separate mountings to maintain the exclusive shape.
* Increase the size of the sign with the exclusive shape so the sign installed on the back does not obscure its shape.
* Increase the mounting height of the sign with the exclusive shape to allow the installation of a back-mounted sign below the bottom edge while still ensuring the minimum required mounting height for the lower sign.
[04] Where the lateral space available in which to install a standard sign is constrained, such as mounting on a narrow median barrier or adjacent to a retaining wall, the following methods should be considered to maintain the shape of the sign:
* Angle the sign up to 45 degrees toward the roadway while still maintaining adequate legibility.
* Install the sign at a different location that still provides adequate advance warning, supplementing the sign with a Distance plaque (see Section 2C.61), if appropriate.
* Reduce the size of the sign, but supplement it with a duplicate sign on the opposite side of the roadway (see Section 2A.11).
* In addition to either angling or reducing the size of the sign, supplement it with a duplicate warning sign and Distance plaque at an upstream location.
* Mount the sign asymmetrically on the sign support, such as when the support is mounted on a bridge parapet or railing, such that the edge of the sign does not overhang the roadway, shoulder, or other areas used by bicyclists or pedestrians.
Option:
[05] Where the shape of the sign cannot be maintained due to lateral constraints, the following methods may be considered:
* For warning signs or other types of signs displayed in a horizontally-oriented rectangle, the legend may be displayed in a vertically-oriented rectangle.
* When mounted overhead, the word legend for a standard warning sign may be displayed in a horizontallyoriented rectangle.
Support:
[06] Provisions for mounting height of signs that overhang any portion of the traveled way are contained in Section 2A.15.
[07] Provisions for lateral offset are contained in Section 2A.16.
Standard:
[08] Modifications to sign shapes, such as cutting off the left and right points of a diamond, shall not be allowed.
Option:
[09] Where the methods described in Paragraph 3 of this Section are impracticable, the legend of the warning sign may be displayed in a vertically-oriented rectangle.
Section 2A.06 Colors
Standard:
[01] The colors to be used on signs and their specific uses on signs shall be as provided in the applicable Sections of this Manual. The color coordinates and values shall be as described in 23 CFR, Part 655, Subpart F, Appendix.
[02] Colors (see Section 1D.05) shall be consistent across the face of a sign or a sign panel. Color gradients (smooth or defined gradual transitions either within a color or transition to another color) shall not be allowed, except as specifically provided in Section 2J.03 for business identification sign panels.
Support:
[03] Common uses of sign colors are shown in Table 2A-2. Color schemes on specific signs are shown in the illustrations located in each applicable Chapter.
[04] Whenever white is specified in this Manual or in the “Standard Highway Signs” publication (see Section 1A.05) as a color, it is understood to include silver-colored retroreflective coatings or elements that reflect white light.
[05] The colors coral and light blue are being reserved for uses that will be determined in the future by the Federal Highway Administration.
[06] Information regarding color coding of destinations on guide signs, including community wayfinding signs, is contained in Chapter 2D.
Option:
[07] The approved fluorescent version of the standard red, yellow, green, or orange color may be used as an alternative to the corresponding standard color.
Section 2A.07 Dimensions
Support:
[01] The “Standard Highway Signs” publication (see Section 1A.05) prescribes design details for different sizes of each sign or plaque depending on the type of traffic facility, including bikeways. Smaller sizes are designed to be used on bikeways and some other off-road applications. Larger sizes are designed for use on freeways and expressways, and can also be used in oversized applications to enhance road user safety and convenience on other facilities, especially on multi-lane divided highways and on undivided highways having five or more lanes of traffic and/or high speeds. The intermediate sizes are designed to be used on other highway types. Minimum sizes of signs and plaques for specific applications are prescribed in the various sign size tables in each Chapter of this Manual.
Standard:
[02] The sign dimensions prescribed in the sign size tables in the various Parts and Chapters in this Manual and in the “Standard Highway Signs” publication (see Section 1A.05) shall be used unless engineering judgment determines that other sizes are appropriate in accordance with the following. Except as provided in Paragraph 3 of this Section, where engineering judgment determines that sizes smaller than the prescribed dimensions are appropriate for use, the sign dimensions shall not be less than the minimum dimensions specified in this Manual. The sizes shown in the Minimum columns that are smaller than the sizes shown in the Conventional Road columns in the various sign size tables in this Manual shall only be used on low-speed roadways, alleys, site roadways open to public travel, and on low-volume rural roads with operating speeds of 30 mph or less; and only where the reduced legend size would be adequate for the regulation or warning or where physical conditions preclude the use of larger sizes. ​
Table 2A-2. Common Uses of Sign Colors :
| Type of Sign | Legend | Legend | Legend | Legend | Legend | Legend | Legend | Legend | Background | Background | Background | Background | Background | Background | Background | Background | Background | Background | Background |
| Type of Sign | Black | Green | Red | White | Yellow | Orange | Fluorescent Yellow-Green | Fluorescent Pink | Black | Blue | Brown | Green | Orange$^1$ | Red$^1$ | White | Yellow$^1$ | Purple | Fluorescent Yellow-Green | Fluorescent Pink |
| Regulatory | X | | X | X | | | | | X | | | | | X | X | | | | |
| Prohibitive | | | X | X$^2$ | | | | | | | | | | X$^2$ | X | | | | |
| Permissive | | X | | | | | | | | | | | | | X | | | | |
| Warning | X | | | | | | | | | | | | | | | X | | | |
| Pedestrian | X | | | | | | | | | | | | | | | X | | X | |
| Bicycle | X | | | | | | | | | | | | | | | X | | X | |
| Guide | | | | X | | | | | | | | X | | | | | | | |
| Interstate Route | | | | X | | | | | | X | | | | X | | | | | |
| State Route | X | | | | | | | | | | | | | | X | | | | |
| U.S. Route | X | | | | | | | | | | | | | | X | | | | |
| County Route | | | | | X | | | | | X | | | | | | | | | |
| Forest Route | | | | X | | | | | | | X | | | | | | | | |
| Street Name | | | | X | | | | | | | | X | | | | | | | |
| Destination | | | | X | | | | | | | | X | | | | | | | |
| Reference Location | | | | X | | | | | | | | X | | | | | | | |
| Information | | | | X | | | | | | X | | X | | | | | | | |
| Evacuation Route | | | | X | | | | | | X | | | | | | | | | |
| Road User Service | | | | X | | | | | | X | | | | | | | | | |
| Recreational | | | | X | | | | | | X | X | | | | | | | | |
| Temporary Traffic Control | X | | | | | | | | | | | | X | | | | | | |
| Incident Management | X | | | | | | | | | | | | X | | | | | | X |
| School | X | | | | | | | | | | | | | | | | | X | |
| ETC-Account Only | X | | | | | | | | | | | | | | | | X$^5$ | | |
| Changeable Message Signs | | | | | | | | | | | | | | | | | | | |
| Regulatory | | | X$^4$ | X | | | | | X | | | | | | | | | | |
| Warning | | | | | X | | | | X | | | | | | | | | | |
| Temporary Traffic Control | | | | | X | X | | | X | | | | | | | | | | |
| Guide | | | | X | | | | | X | | | X$^3$ | | | | | | | |
| Motorist Services | | | | X | | | | | X | X$^3$ | | | | | | | | | |
| Incident Management | | | | | X | | | X | X | | | | | | | | | | |
| School, Pedestrian, Bicycle | | | | | X | | X | | X | | | | | | | | | | |
$^1$ Fluorescent versions of these background colors may also be used.
$^2$ Legend and background color combination for use only as identified for specific signs in this Manual or Standard Highway Signs.
$^3$ These alternative background colors would be provided by blue or green lighted pixels such that the entire CMS would be lighted, not just the legend.
$^4$ Red is used only for the circle and diagonal or other red elements of a similar static regulatory sign.
$^5$ The use of purple on signs is restricted per the provisions of Chapter 2F.
Notes:
* The purpose of the information in this table is to provide a general overview of common color combinations. The color combinations and orientations for signs with standardized designs shall not be modified. For signs with unique legends, the shape and color shall be the same as standard signs of the same functional type.
* The colors shown for changeable message signs are for those with electronic displays. ​
Option:
[03] For alleys with restrictive physical conditions and vehicle use that limits installation of the Minimum size sign (or the Conventional Road size sign if no Minimum size is shown), both the sign height and the sign width may be decreased by up to 6 inches.
Guidance:
[04] The sizes shown in the Freeway and Expressway columns in the various sign size tables in this Manual should also be used for other higher-speed applications on conventional roads, based upon engineering judgment, to provide larger signs for increased visibility and recognition.
[05] The sizes shown in the Oversized columns in the various sign size tables in this Manual should be used for those special applications where speed, volume, or other factors result in conditions where increased emphasis, improved recognition, or increased legibility is needed, as determined by engineering judgment or study.
[06] Except as provided in Paragraph 7 of this Section, and where specifically prohibited in this Manual, increases above the minimum prescribed sizes should be used where greater legibility or emphasis is needed. If signs larger than the prescribed sizes are used, the overall sign dimensions should be increased in 6-inch increments.
Standard:
[07] Where a maximum allowable sign size is prescribed, increases in sign size above the maximum size shall not be allowed.
[08] Where engineering judgment determines that sizes that are different from the minimum prescribed dimensions are appropriate for use, standard shapes and colors shall be used. Standard proportions shall be retained as much as practicable.
Guidance:
[09] Except where specifically prohibited in this Manual, when supplemental plaques are installed with largersized signs, a corresponding increase in the size of the plaque and its legend should also be made. The resulting plaque size should be approximately in the same relative proportion to the larger-sized sign as the conventional-sized plaque is to the conventional-sized sign.'
Standard:
[01] Except as otherwise provided in this Manual, all word messages shall be aligned horizontally across a sign, reading left to right.
[02] Except as provided in Section 2A.04, all word messages shall use standard wording as shown in this Manual and in the “Standard Highway Signs” publication (see Section 1A.05).
[03] All sign lettering, numerals, and other characters shall be of the Standard Alphabets as provided in the “Standard Highway Signs” publication (see Section 1A.05), unless otherwise provided in this Manual.
[04] The sign lettering for names of places, streets, and highways shall be composed of a combination of lower-case letters with initial upper-case letters. The sign lettering for other legends shall be composed of upper-case letters, unless otherwise provided in this Manual for a particular sign or type of message.
[05] Except as provided in Chapter 2E of this Manual, when a mixed-case legend is used, the nominal loop height of the lower-case letters shall be ¾ of the height of the initial upper-case letter.
[06] The unique letter forms for each of the Standard Alphabet series shall not be stretched, compressed, warped, or otherwise manipulated.
Support:
[07] Section 2D.03 contains information regarding the acceptable methods of modifying the length of a word for a given letter height and series.
Guidance:
[08] Word messages should be as brief as practical to convey a clear, simple meaning, and the lettering should be large enough to provide the necessary legibility distance. A minimum specific ratio of 1 inch of letter height per 30 feet of legibility distance should be used.'
[09] Abbreviations (see Section 1D.08) should be kept to a minimum, except as otherwise prescribed in this Manual.
Support:
[11] Diacritical marks on words or names that are adapted to English are not normally needed on signs for comprehension or navigational purposes.
Option:
[12] A legend in a secondary language, in addition to English, may be displayed on the face of signs, plaques, sign panels, and changeable message signs that are oriented away from or otherwise not readily visible to operators of motor vehicles, but rather are intended for viewing only by pedestrians and occupants of parked vehicles.
Guidance:
[13] The solidus (slanted line or forward slash) is intended to be used for fractions only and should not be used to separate words on the same line of legend. Instead, a hyphen should be used for this purpose, such as “TRUCKS - BUSES.”
Standard:
[14] Fractions shall be displayed with the numerator and denominator diagonally arranged about the solidus. The overall height of the fraction is measured from the top of the numerator to the bottom of the denominator, each of which is vertically aligned with the upper and lower ends of the solidus. The overall height of the fraction shall be determined by the height of the numerals within the fraction, and shall be 1.5 times the height of an individual numeral within the fraction.
[15] Except as otherwise provided in this Manual, distances shall be displayed on signs using fractions of a mile rather than decimals.
Support:
[16] The “Standard Highway Signs” publication (see Section 1A.05) contains details regarding the layouts of fractions on signs.
Guidance:
[17] When initials are used to represent an abbreviation for separate words (such as “U S” for a United States route), the initials should be separated by a space of between ½ and ¾ of the letter height of the initials.
[18] When an Interstate route is displayed in text form instead of using the route shield, a hyphen should be used for clarity, such as “I-50.”
Support:
[19] Letter height is expressed in terms of the height of an upper-case letter. For mixed-case legends (those composed of an initial upper-case letter followed by lower-case letters), the height of the lower-case letters is derived from the specified height of the initial upper-case letter based on a prescribed ratio. Letter heights for mixed-case legends might be expressed in terms of both the upper- and lower-case letters, or in terms of the initial uppercase letter alone. When the height of a lower-case letter is specified or determined from the prescribed ratio, the reference is to the nominal loop height of the letter. The term loop height refers to the portion of a lower-case letter that excludes any ascending or descending stems or tails of the letter, such as with the letters “d” or “q.” The nominal loop height is equal to the actual height of a non-rounded lower-case letter whose form does not include ascending or descending stems or tails, such as the letter “x.” The rounded portions of a lower-case letter extend slightly above and below the baselines projected from the top and bottom of such a non-rounded letter so that the appearance of a uniform letter height within a word is achieved. The actual loop height of a rounded lower-case letter is slightly greater than the nominal loop height and this additional height is excluded from the expression of the lower-case letter height.
Section 2A.09 Symbols
Standard:
[01] Symbol designs shall in all cases be unmistakably similar to those shown in this Manual and in the “Standard Highway Signs” publication (see Section 1A.05).
Option:
[02] Although most standard symbols are oriented facing left, mirror images of these symbols may be used where the reverse orientation might better convey to road users a direction of movement.
Support:
Option:
[04] State and/or local highway agencies may conduct research studies to determine road user comprehension, sign conspicuity, and sign legibility in compliance with the provisions for official experimentation (see Section 1B.05) when a new symbol design is under consideration.
Support: [05] Sometimes a change from word messages to symbols requires significant time for public education and transition. Therefore, this Manual sometimes includes the practice of using educational plaques to accompany new symbol signs.
Guidance:
[06] New standard warning or regulatory symbol signs should be accompanied by an educational plaque where engineering judgment determines that the plaque will improve road user comprehension during the transition from word message to symbol signs.
Option:
[07] Educational plaques may be left in place as long as they are in serviceable condition.
Standard:
[08] A symbol used for a given category of signs (regulatory, warning, or guide) shall not be used for a different category of signs, except as specifically authorized in this Manual.
[09] A recreational and cultural interest area symbol (see Chapter 2M) shall not be used on streets or highways outside of recreational and cultural interest areas.
[10] A recreational and cultural interest area symbol (see Chapter 2M) shall not be used on any regulatory or warning sign on any street, road, or highway.
Support:
[11] Section 2M.07 contains provisions for the use of recreational and cultural interest area symbols to indicate prohibited activities or items in non-road applications.
Section 2A.10 Sign Borders
Standard:
[01] Unless otherwise provided, signs shall have a border of the same color as the legend in order to outline their distinctive shape and thereby give them easy recognition and a finished appearance.
[02] The corners of all sign borders shall be rounded, except for STOP signs.
Guidance:
[03] A dark border on a light background should be set in from the edge, while a light border on a dark background should extend to the edge of the sign. A border for 30-inch signs with a light background should be from ½ to ¾ inch in width, ½ inch from the edge. For similar signs with a light border, a width of 1 inch should be used. For other sizes, the border width should be of similar proportions, but should not exceed the stroke-width of the major lettering of the sign. On signs exceeding 72 x 120 inches in size, the border should be 2 inches wide. On unusually large signs with oversized letter heights, route shields, or other legend elements, the border should be 2.5 inches wide and should not exceed 3 inches in width. Except for STOP signs and as otherwise provided in Section 2E.14, the corners of the sign should be rounded to a radius that is concentric with that of the border.
Support:
[04] Section 2A.12 contains information regarding the use of light-emitting diode (LED) units within the border of a sign.
Section 2A.11 Enhanced Conspicuity for Standard Signs
Option:
[01] Based upon engineering judgment, where the improvement of the conspicuity of a standard regulatory, warning, or guide sign is desired, any of the following methods may be used, as appropriate, to enhance the sign’s conspicuity (see Figure 2A-1):
* Increasing the size of a standard regulatory, warning, or guide sign.
* Dual signing of a standard regulatory, warning, or guide sign by adding a second identical sign on the left-hand side of the roadway at the same location.
* Adding a solid yellow or fluorescent yellow rectangular header panel above a standard regulatory sign, with the width of the panel corresponding to the width of the standard regulatory sign. A legend of “NOTICE,” “STATE LAW,” or other appropriate text may be added in black letters within the header panel for a period of time determined by engineering judgment.
* Adding a NEW plaque (see Section 2C.60) above a new standard regulatory or warning sign, for a period of time in accordance with Paragraph 3 of this Section, to call attention to the new sign.
Figure 2A-1. Examples of Enhanced Conspicuity for Signs
* Adding one or more red or orange flags (cloth or retroreflective sheeting) above a standard regulatory or warning sign, with the flags oriented at 45 degrees to the vertical.
* Adding a solid yellow, a solid fluorescent yellow, or a diagonally-striped black and yellow (or black and fluorescent yellow) strip of retroreflective sheeting at least 3 inches wide around the perimeter of a standard warning sign. This may be accomplished by affixing the standard warning sign on a background that is 6 inches larger than the size of the standard warning sign.
* Adding a Warning Beacon (see Section 4S.03) to a standard regulatory (other than a STOP, DO NOT ENTER, WRONG WAY, or a Speed Limit sign), warning, or guide sign.
* Adding a Speed Limit Sign Beacon (see Section 4S.04) to a standard Speed Limit sign.
* Adding a Stop Beacon (see Section 4S.05) to a STOP, DO NOT ENTER, or WRONG WAY sign.
* Adding a rectangular rapid-flashing beacon (see Chapter 4L) to a Pedestrian, School, or Trail warning sign at an uncontrolled marked crosswalk.
* Adding light-emitting diode (LED) units within the symbol, legend, or border of a standard regulatory, warning, or guide sign, as provided in Section 2A.12.
* Adding a strip of retroreflective material to the sign support in accordance with the provisions of Paragraph 5 of this Section.
* Using other methods that are specifically allowed for certain signs as described elsewhere in this Manual.
Support:
[02] Sign conspicuity improvements can also be achieved by removing non-essential and illegal signs from the right-of-way (see Section 1D.02), and by relocating signs to provide better spacing. Section 2A.20 contains information on excessive use of signs.
Guidance:
[03] If a NEW plaque is used, it should remain in place for a period of time determined by engineering judgment, but not more than 12 months.
Standard:
[04] Strobe lights shall not be used to enhance the conspicuity of highway signs.
[05] If a strip of retroreflective material is used on the sign support, it shall be at least 2 inches in width, it shall be placed for the full length of the support from the sign to within 2 feet above the near edge of the roadway, and its color shall match the background color of the sign, except that the color of the strip for the YIELD and DO NOT ENTER signs shall be red. The retroreflective strip shall not display any legend or other information.
[06] For a post-mounted sign installation, placing a duplicate sign in the same assembly facing the same direction of traffic shall not be permitted as a method of enhancing conspicuity.
Section 2A.12 LEDs Used for Conspicuity Enhancement on Standard Signs
Support:
[01] This Section regarding light-emitting diode (LED) units applies to the use of illuminated elements that supplement a sign legend to enhance the conspicuity of the sign.
[02] LED units that are used to illuminate the full sign display, background, or legend are changeable message signs (CMS), which are covered in Chapters 2B, 2C, and 2L, and Part 7.
[03] The application of LED units in compliance with Paragraph 8 of this Section does not create a changeable message sign because the legend of the sign is always displayed when the LED units are not illuminated. Changeable message or blank-out signs whose legends change or extinguish by means of illuminated elements are addressed elsewhere in this Manual.
Option:
[04] Light-emitting diode (LED) units may be used individually within the symbol, legend, or border of a sign to enhance the sign conspicuity and legibility (see Section 2A.11).
[05] Except as provided in Paragraph 11 of this Section, LED units may either operate continuously or be actuated.
Standard:
[06] Where LED units are used to enhance the conspicuity of a sign, the sign shall otherwise comply with the requirements for retroreflection and illumination for nighttime viewing (see Section 2A.21).
[07] Except as provided in Paragraphs 16 and 17 of this Section, and for changeable message signs, neither individual LEDs nor groups of LEDs shall be placed within the background area of a sign.
[09] The LEDs shall not protrude outside the sign border or legend when used in such applications, shall have a maximum diameter of ¼ inch, and shall be the following colors based on the type of sign:
* White or red, with STOP, YIELD, DO NOT ENTER, or WRONG WAY signs.
* White, with other regulatory signs.
* White or yellow, with warning signs.
* White or green, with guide signs.
* White, yellow, or orange, with temporary traffic control signs.
* White, yellow, or fluorescent yellow-green, with school area or pedestrian or bicycle warning signs.
[10] If flashed, all LED units shall flash simultaneously at a steady rate between 50 and 60 times per minute. All the LED units in a sign legend or border shall be illuminated simultaneously with no sequential (chasing) or variable flash rates (dancing), except as otherwise allowed in this Manual. A cluster of LEDs shall not be used within the border of a sign.
[11] Where used in STOP or YIELD signs, flashing LED units shall operate continuously. Actuation of the LED units shall not be allowed.
[12] Flashing LED units shall not be used within the legend or border of a Speed Limit sign to indicate that the displayed speed limit is in effect.
[13] LED units shall not be used within the legend or border of a sign in conjunction with the phrase WHEN FLASHING in its legend or on a supplemental WHEN FLASHING plaque (see Item E in Paragraph 1 of Section 4S.03 for the use of Warning Beacons to indicate when a regulatory or warning message is in effect).
[14] Where LED units are used along the edge of a sign, at least one LED unit shall be placed along each edge of the sign, in addition to one LED unit at each corner of the sign, so that the distinct outline of the sign shape is recognized under nighttime viewing conditions. The LED units along each side of the sign shall be spaced approximately equidistantly. For a circular sign shape, the number of LED units shall clearly form the appearance of a circle and not be perceived as some other shape.
[15] The uniformity of the sign design shall be maintained without any decrease in visibility, legibility, or driver comprehension during either daytime or nighttime conditions. The LED units shall have the capability to be dimmed automatically by a timing mechanism or a device sensitive to ambient light (photoelectric cell) such that the LEDs do not reduce the visibility of the sign legend.
Option:
[16] For STOP, YIELD, DO NOT ENTER, and WRONG WAY signs, LEDs may be placed within the border or within one border width within the background of the sign.
Support:
[17] Section 6D.02 contains information about STOP/SLOW paddles used by flaggers. Section 7D.02 contains information about STOP paddles used by adult crossing guards.
[18] Other methods of enhancing the conspicuity of standard signs are described in Section 2A.11.
Section 2A.13 Standardization of Location
Support:
[01] Standardization of position cannot always be attained in practice. Examples of heights and lateral locations of signs for typical installations are illustrated in Figure 2A-2, and examples of locations for some typical signs at intersections are illustrated in Figure 2A-3 and all four sheets in Figure 2A-4.
[02] Examples of advance signing on intersection approaches are illustrated in all four sheets in Figure 2A-4. Chapters 2B, 2C, and 2D contain provisions regarding the application of regulatory, warning, and guide signs, respectively.
Standard:
[03] Signs requiring separate decisions by the road user shall be spaced sufficiently far apart for the appropriate decisions to be made.
Guidance:
[04] One of the factors considered when determining the appropriate spacing of signs should be the posted or 85th-percentile speed.
[05] Except as provided in Paragraph 8 of this Section, signs should be located on the right-hand side of the roadway where they are easily recognized and understood by road users. Signs in other locations should be considered only as supplementary to signs in the normal locations, except as otherwise provided in this Manual.
[06] Signs should be individually installed on separate posts or mountings except where:
Figure 2A-2. Examples of Heights and Lateral Locations of Sign Installations
Figure 2A-3. Examples of Locations for Some Typical Signs at Intersections
Figure 2A-4. Relative Locations of Regulatory, Warning, and Guide Signs on an Intersection Approach (Sheet 1 of 4)
Figure 2A-4. Relative Locations of Regulatory, Warning, and Guide Signs on an Intersection Approach (Sheet 2 of 4)
Figure 2A-4. Relative Locations of Regulatory, Warning, and Guide Signs on an Intersection Approach (Sheet 3 of 4)
Figure 2A-4. Relative Locations of Regulatory, Warning, and Guide Signs on an Intersection Approach (Sheet 4 of 4)
* Route or directional signs are grouped to clarify information to motorists;
* Regulatory signs that do not conflict with each other are grouped, such as Turn Prohibition signs posted with ONE WAY signs or a parking regulation sign posted with a Speed Limit sign; or
* Street Name signs are posted with a STOP or YIELD sign.
[07] Signs should be located so that they:
* Are outside the clear zone unless placed on a crashworthy (see definition in Section 1C.02) support,
* Optimize nighttime visibility,
* Minimize the effects of mud splatter and debris,
* Do not obscure each other,
* Do not obscure the sight distance to approaching vehicles on the major street for drivers who are stopped on minor-street approaches, and
* Are not hidden from view.
[08] Except for STOP, YIELD, DO NOT ENTER, and WRONG WAY signs, or as otherwise provided in this Manual, where a sign on a one-way roadway indicates an action intended exclusively or primarily for a road user in the left-hand lane or at the left-hand side of that roadway, such as LEFT LANE MUST TURN LEFT (R3-7) or LEFT LANE ENDS (W9-1), the sign should be located on the left-hand side of the roadway. In the case of a divided road, the sign should be located in the median.
Option:
[09] Signs located on the left-hand side of a one-way roadway or in the median of a divided road, in accordance with Paragraph 8 of this Section, may be supplemented by an identical sign located on the right-hand side of the roadway.
Support:
[10] The clear zone (see definition in Section 1C.02) is the total roadside border area, starting at the edge of the traveled way, available for an errant driver to stop or regain control of a vehicle. The width of the clear zone is dependent upon traffic volumes, speeds, and roadside geometry. Additional information can be found in the “Roadside Design Guide,” 4th Edition, 2011, AASHTO.
Guidance:
[11] With the increase in traffic volumes and the need to provide road users regulatory, warning, and guidance information, an order of priority for sign installation should be established.
Support:
[12] An order of priority is especially critical where space is limited for sign installation and there is a demand for several different types of signs. Overloading road users with too much information is not desirable. Priority according to type of sign will depend on the specific situation and conditions of the site at which the signs are to be installed. For example, in the vicinity of an exit ramp, guide signs and warning signs for the exit ramp might take precedence over regulatory signs that confirm rules of the road, such as a STATE LAW-NO HANDHELD PHONE USE BY DRIVER sign, or a mainline Speed Limit sign where there is no change in the speed zone.
Guidance:
[13] Because regulatory and warning information is typically more critical to the road user than guidance information, regulatory and warning signing whose locations are critical should be displayed rather than guide signing in cases where conflicts occur. In such cases, the guide sign should be relocated to another appropriate location where it will still be effective. In other cases, such as at a decision point, the guide sign should take precedence over other signs whose locations are not as critical to an immediate decision or action necessary by the road user. In all cases, careful attention should be given to minimizing sign clutter (see Section 2A.20). Community wayfinding and acknowledgment guide signs should have a lower priority as to placement than other guide signs. Signs conveying information of a less-critical nature should be moved to less-critical locations or omitted.
Option:
[14] Under some circumstances, such as on curves to the right, signs may be placed on median islands or on the left-hand side of the road. A supplementary sign located on the left-hand side of the roadway may be used on a multi-lane road where traffic in a lane to the right might obstruct the view to the right.
Guidance:
Section 2A.14 Overhead Sign Installations
Guidance:
[01] Overhead signs should be used on freeways and expressways, at locations where some degree of lane-use control is desirable, and at locations where space is not available at the roadside.
Support:
[02] The operational requirements of the present highway system are such that overhead signs have value at many locations. The factors to be considered for the installation of overhead sign displays are not definable in specific numerical terms. In some cases, overhead mounting of a sign might be required by other provisions of this Manual.
Option:
[03] The following conditions (not in priority order) may be considered in an engineering study to determine if overhead signs would be beneficial:
* Traffic volume at or near capacity,
* Complex interchange design,
* Three or more lanes in each direction,
* Restricted sight distance,
* Closely-spaced interchanges,
* Multi-lane exits,
* Large percentage of trucks,
* Street lighting background,
* High-speed traffic,
* Consistency of sign message location through a series of interchanges,
* Insufficient space for post-mounted signs,
* Junction of two freeways, and
* Left-side exit ramps.
[04] Over-crossing structures may be used to support overhead signs.
Support:
[05] Under some circumstances, the use of over-crossing structures as sign supports might be the only practical solution that will provide adequate viewing distance. The use of such structures as sign supports might eliminate the need for the foundations and sign supports along the roadside.
Section 2A.15 Mounting Height
Standard:
[01] The provisions of this Section shall apply unless specifically stated otherwise for a particular sign or object marker elsewhere in this Manual.
Support:
[02] It might be necessary to use larger minimum mounting heights than those prescribed in this Manual to ensure appropriate crash performance of sign installations that are required to be crashworthy (see Section 1D.11).
[03] In addition to the provisions of this Section, information affecting the minimum mounting height of signs as a function of crash performance can be found in the “Roadside Design Guide,” 4th Edition, 2011, AASHTO.
Standard:
[04] In rural areas, the minimum height, measured vertically from the bottom of the sign to the elevation of the near edge of the pavement, of signs installed at the side of the road shall be 5 feet (see Figure 2A-2).
[05] In business, commercial, or residential areas where parking, bicyclist, or pedestrian movements are likely to occur, or where the view of the sign might be obstructed, the minimum height, measured vertically from the bottom of the sign to the top of the curb, or in the absence of curb, measured vertically from the bottom of the sign to the elevation of the near edge of the traveled way, of signs installed at the side of the road shall be 7 feet (see Figure 2A-2).
Option:
[06] The height to the bottom of a secondary sign mounted below another sign may be 1 foot less than the height specified in Paragraphs 4 and 5 of this Section.
Standard:
[08] If the bottom of a secondary sign that is mounted below another sign is mounted lower than 7 feet above a pedestrian sidewalk or pathway (see Section 6C.02), the secondary sign shall not project more than 4 inches into the pedestrian facility.
Support:
[09] Section 9A.02 contains provisions for the minimum mounting height of signs on shared-use paths.
Option:
[10] Signs that are placed 30 feet or more from the edge of the traveled way may be installed with a minimum height of 5 feet, measured vertically from the bottom of the sign to the elevation of the near edge of the pavement.
Standard:
[11] Directional signs on freeways and expressways shall be installed with a minimum height of 7 feet, measured vertically from the bottom of the sign to the elevation of the near edge of the pavement. All route signs, warning signs, and regulatory signs on freeways and expressways shall be installed with a minimum height of 7 feet, measured vertically from the bottom of the sign to the elevation of the near edge of the pavement. If a secondary sign is mounted below another sign on a freeway or expressway, the major sign shall be installed with a minimum height of 8 feet and the secondary sign shall be installed with a minimum height of 5 feet, measured vertically from the bottom of the sign to the elevation of the near edge of the pavement.
[12] Where large signs having an area exceeding 50 square feet are installed on multiple breakaway posts, the clearance from the ground to the bottom of the sign shall be at least 7 feet.
Option:
[13] A route sign assembly (see Section 2D.29) consisting of a route sign and auxiliary signs may be treated as a single sign for the purposes of this Section.
[14] The mounting height may be adjusted when supports are located near the edge of the right-of-way on a steep backslope in order to avoid the sometimes less desirable alternative of placing the sign closer to the roadway.
Standard:
[15] Signs that are post-mounted on a median barrier that overhang any portion of the traveled way shall be mounted with a vertical clearance that complies with that of overhead signs.
[16] Overhead signs shall provide a vertical clearance of not less than 17 feet to the sign, light fixture, or sign bridge over the entire width of the pavement and shoulders, except where the structure on which the overhead signs are to be mounted or other structures along the roadway near the sign structure have a lesser vertical clearance.
Option:
[17] If the vertical clearance of other structures along the roadway near the sign structure is less than 16 feet, the vertical clearance to an overhead sign structure or support may be as low as 1 foot higher than the vertical clearance of the other structures in order to improve the visibility of the overhead signs.
[18] In special cases the clearance to overhead signs may be reduced if necessary because of substandard dimensions in tunnels and other major structures such as double-deck bridges.
Guidance:
[19] While a maximum mounting height for signs is generally not prescribed in this Manual, agencies should ensure that signs are not mounted at such a height as to be out of the road user’s normal field of vision (see Paragraph 3 of Section 1D.09), especially in urban settings where signs are mounted on traffic signal or light poles.
Support:
[20] Figure 2A-2 illustrates some examples of the mounting height requirements contained in this Section.
Section 2A.16 Lateral Offset
Standard:
[01] For overhead sign supports, the minimum lateral offset from the edge of the shoulder (or if no shoulder exists, from the edge of the pavement) to the near edge of overhead sign supports (cantilever or sign bridges) shall be 6 feet. Overhead sign supports shall have a barrier or crash cushion to shield them if they are within the clear zone.
Guidance:
[03] For post-mounted signs, the minimum lateral offset should be 12 feet from the edge of the traveled way. If a shoulder wider than 6 feet exists, the minimum lateral offset for post-mounted signs should be 6 feet from the edge of the shoulder.
[04] Supports for signs mounted laterally behind a longitudinal barrier should be placed so that the near edge of the support is located beyond the deflection distance of the longitudinal barrier.
Support:
[05] The minimum lateral offset requirements for object markers are provided in Chapter 2C.
[06] The minimum lateral offset is intended to keep trucks and cars that use the shoulders from striking the signs or supports. The minimum lateral offset requirements do not supersede the requirement for crashworthiness (see Paragraph 2 of this Section) if the sign is located within the clear zone.
Guidance:
[07] All supports should be located as far as practical from the edge of the shoulder. Advantage should be taken to place signs behind existing roadside barriers, on over-crossing structures, or other locations that minimize the exposure of the traffic to sign supports.
Option:
[08] Lesser lateral offsets may be used on connecting roadways or ramps at interchanges, but not less than 6 feet from the edge of the traveled way.
[09] On conventional, low-volume rural, and special-purpose roads in areas where it is impractical to locate a sign with the lateral offset prescribed by this Section because of roadside features such as terrain or vegetation, a lateral offset of at least 2 feet may be used.
[10] A lateral offset of at least 1 foot from the face of the curb may be used in business, commercial, or residential areas where sidewalk width is limited or where existing poles are close to the curb.
Guidance:
[11] Overhead sign supports and post-mounted sign and object marker supports should not intrude into the usable width of a sidewalk or other pedestrian facility.
Support:
[12] Guidance for maintaining sign shape in laterally-constrained conditions is described in Section 2A.05.
[13] Figures 2A-2 and 2A-3 illustrate some examples of the lateral offset requirements contained in this Section.
Section 2A.17 Orientation
Guidance:
[01] Unless otherwise provided in this Manual, signs should be vertically mounted at right angles to the direction of, and facing, the traffic that they are intended to serve.
[02] Where mirror reflection from the sign face is encountered to such a degree as to reduce legibility, the sign should be turned slightly away from the road. Signs that are placed 30 feet or more from the pavement edge should be turned toward the road. On curved alignments, the angle of placement should be determined by the direction of approaching traffic rather than by the roadway edge at the point where the sign is located.
Option:
[03] On grades, sign faces may be tilted forward or back from the vertical position to improve the viewing angle.
Section 2A.18 Posts and Mountings
Standard:
[01] Sign posts, foundations, and mountings shall be so constructed as to hold signs in a proper and permanent position, and to resist swaying in the wind or displacement by vandalism.
Support:
[02] The latest edition of AASHTO’s “Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals” contains additional information regarding posts and mounting.
Option:
[03] Where permitted, signs may be placed on existing supports used for other purposes, such as highway traffic signal supports, highway lighting supports, and utility poles.
Support:
[04] Section 2A.11 contains criteria for enhanced conspicuity of standard signs.
Standard:
[06] If mounted to the sign support, equipment for powering electronic components of a sign, including solar panels, shall be mounted so as not to compromise the crashworthy performance of the sign installation (see Section 1D.11). Such equipment shall be mounted so as not to obscure the shape of the sign.
Section 2A.19 Maintenance
Guidance:
[01] Maintenance activities should consider proper position, cleanliness, legibility, and daytime and nighttime visibility (see Sections 2A.21 and 2A.22). Damaged or deteriorated signs, gates, or object markers should be replaced.
[02] To assure adequate maintenance, a schedule for inspecting (both day and night), cleaning, and replacing signs, gates, and object markers should be established. Employees of highway, law enforcement, and other public agencies whose duties require that they travel on the roadways should be encouraged to report any damaged, deteriorated, or obscured signs, gates, or object markers at the first opportunity.
[03] Steps should be taken to see that weeds, trees, shrubbery, and construction, maintenance, and utility materials and equipment do not obscure the face of any sign or object marker.
[04] A regular schedule of replacement of lighting elements for illuminated signs should be maintained.
Section 2A.20 Excessive Use of Signs
Guidance:
[01] Signs should be used and located judiciously, minimizing their proliferation in order to maintain their effectiveness. Regulatory and warning signs should be used conservatively because these signs, if used to excess, tend to lose their effectiveness. Route signs and directional guide signs for primary routes and destinations should be used frequently at strategic locations because their use promotes efficient operations by keeping road users informed of their location. In all cases, however, sign clutter (see Paragraph 2 of this Section) should be avoided and minimized as much as practicable.
Support:
[02] Sign clutter is the proliferation of sign installations or assemblies along the roadway or roadside, either separately or grouped, to such an extent that adequate spacing between installations necessary for orderly processing of the sign messages by the driver cannot be achieved. Sign clutter can reduce the effectiveness of one or more signs in a sequence of signs.
[03] The basic role of traffic control devices is to provide only as much information to the road user as necessary to promote the safe and efficient operation of streets and highways. Sign clutter can result from the overuse of MUTCD-compliant signs and or signs that display information unrelated to traffic operation, navigation, or transportation information. Examples of such signs would include, but are not limited to, those displaying the birthplace or home of a noted person, local sports team accomplishments, population information, and self-described qualities of a community such as “friendly” or “open for business.”
Guidance:
[04] Signs and other traffic control devices should be installed and maintained from a systematic standpoint rather than individually. When a new sign is installed, the existing signs in the vicinity should be considered for replacement, relocation, or removal as a result of the new sign that is installed. Existing systems of signs should be reviewed periodically for evidence of sign clutter and adjustments should be made accordingly.
Support:
[05] Section 2A.13 contains information regarding an order of priority for signs where available spacing along the roadway is limited.
Section 2A.21 Retroreflection and Illumination
Support:
[01] There are many materials currently available for retroreflection and various methods currently available for the illumination of signs and object markers. New materials and methods continue to emerge. New materials and methods can be used as long as the signs and object markers meet the standard requirements for color, both by day and by night.
Standard:
[03] Regulatory, warning, and guide signs (see Section 2A.03), and object markers, shall be retroreflective or illuminated to show the same shape and similar color by both day and night, unless otherwise provided in this Manual for a particular sign or group of signs.
[04] Where the color black is specified for the legend or background of a sign, an opaque and nonretroreflective material shall be used.
[05] The requirements for sign illumination shall not be considered to be satisfied by street or highway lighting.
Table 2A-3. Illumination of Sign Elements :
| Means of Illumination | Sign Element to be Illuminated |
| Light behind the sign face | Symbol or word message Background Symbol, word message, and background (through a translucent material) |
| Attached or independently-mounted light source designed to direct essentially uniform illumination onto the sign face | Entire sign face |
| Light-emitting diodes (LEDs) | Symbol or word message Entire sign border |
| Other devices or treatments that highlight the sign shape, color, or message: Luminous tubing Fiber optics Incandescent light bulbs Luminescent panels | Symbol or word message Entire sign face |
Table 2A-4. Retroreflection of Sign Elements :
| Means of Retroreflection | Sign Element |
| Prismatic reflector “buttons” or similar units | Symbol Word message Border |
| A material that has a smooth, sealed outer surface over a microstructure that reflects light | Symbol Word message Border Background |
Option:
[06] Sign elements may be illuminated by the means shown in Table 2A-3.
[07] Retroreflection of sign elements may be accomplished by the means shown in Table 2A-4.
Support:
[08] Information regarding the use of retroreflective material on the sign support is contained in Section 2A.11.
Section 2A.22 Maintaining Minimum Retroreflectivity
Support:
[01] Retroreflectivity is one of several factors associated with maintaining nighttime sign visibility (see Section 2A.21).
Standard:
[02] Public agencies or officials having jurisdiction shall use an assessment or management method that is designed to maintain sign retroreflectivity at or above the minimum levels in Table 2A-5.
Support:
[03] Compliance with the Standard in Paragraph 2 of this Section is achieved by having a method in place and using the method to maintain the minimum levels established in Table 2A-5. Provided that an assessment or management method is being used, an agency or official having jurisdiction would be in compliance with the Standard in Paragraph 2 of this Section even if there are some individual signs that do not meet the minimum retroreflectivity levels at a particular point in time.
Guidance:
[04] Except for those signs specifically identified in Paragraph 5 of this Section, one or more of the methods described in “Maintaining Traffic Sign Retroreflectivity,” (FHWA-SA-07-020, Revised 2013), FHWA, or a method developed based on an engineering study, should be used to maintain sign retroreflectivity at or above the minimum levels in Table 2A-5. Signs that are identified through the agency’s method as being below the minimum levels should be replaced.
Option:
[05] Highway agencies may exclude the following signs from the retroreflectivity maintenance guidelines described in this Section:
* Parking, Standing, and Stopping (R7 and R8 series) signs;
* Walking/Hitchhiking/Crossing (R9 series, R10-1 through R10-4b) signs;
* Acknowledgment signs; and
* Bikeway signs that are intended for exclusive use by bicyclists or pedestrians.
Table 2A-5. Minimum Maintained Retroreflectivity Levels$^1$ :
| Sign Color | Beaded Sheeting Type (ASTM D4956) | Beaded Sheeting Type (ASTM D4956) | Beaded Sheeting Type (ASTM D4956) | Prismatic Sheeting | Prismatic Sheeting | Additional Criteria |
| Sign Color | I | II | III | Prismatic Sheeting | Prismatic Sheeting | Additional Criteria |
| White on Green | W$^*$; G ≥ 7 | W$^*$; G ≥ 15 | W$^*$; G ≥ 25 | W ≥ 250; G ≥ 25 | W ≥ 250; G ≥ 25 | Overhead |
| White on Green | W$^*$; G ≥ 7 | W ≥ 120; G ≥ 15 | W ≥ 120; G ≥ 15 | W ≥ 120; G ≥ 15 | W ≥ 120; G ≥ 15 | Post-mounted |
| White on Blue | W$^*$; B ≥ 3 | W$^*$; B ≥ 5 | W$^*$; B ≥ 12 | W ≥ 250; B ≥ 12 | W ≥ 250; B ≥ 12 | Overhead |
| White on Blue | W$^*$; B ≥ 3 | W ≥ 120; B ≥ 7 | W ≥ 120; B ≥ 7 | W ≥ 120; B ≥ 7 | W ≥ 120; B ≥ 7 | Post-mounted |
| White on Brown | W$^*$; Br ≥ 1 | W$^*$; Br ≥ 5 | W$^*$; Br ≥ 10 | W ≥ 350; Br ≥ 10 | W ≥ 350; Br ≥ 10 | Overhead |
| White on Brown | W$^*$; Br ≥ 1 | W ≥ 150; Br ≥ 5 | W ≥ 150; Br ≥ 5 | W ≥ 150; Br ≥ 5 | W ≥ 150; Br ≥ 5 | Post-mounted |
| Black on Yellow or Black on Orange | Y$^*$; O$^*$ | Y ≥ 50; O ≥ 50 | Y ≥ 50; O ≥ 50 | Y ≥ 50; O ≥ 50 | Y ≥ 50; O ≥ 50 | $^2$ |
| Black on Yellow or Black on Orange | Y$^*$; O$^*$ | Y ≥ 75; O ≥ 75 | Y ≥ 75; O ≥ 75 | Y ≥ 75; O ≥ 75 | Y ≥ 75; O ≥ 75 | $^3$ |
| White on Red | W ≥ 35; R ≥ 7 | W ≥ 35; R ≥ 7 | W ≥ 35; R ≥ 7 | W ≥ 35; R ≥ 7 | W ≥ 35; R ≥ 7 | $^4$ |
| Black on White | W ≥ 50 | W ≥ 50 | W ≥ 50 | W ≥ 50 | W ≥ 50 | – |
| $^1$ The minimum maintained retroreflectivity levels shown in this table are in units of cd/lx/m2 measured at an observation angle of 0.2° and an entrance angle of -4.0°. $^2$ For word legend and fine symbol signs measuring at least 48 inches and for all sizes of bold symbol signs $^3$ For word legend and fine symbol signs measuring less than 48 inches $^4$ Minimum sign contrast ratio ≥ 3:1 (white retroreflectivity ÷ red retroreflectivity) $^*$ This sheeting type shall not be used for this color for this application |||||||
| Bold Symbol Signs |||||||
| W1-1,2 – Turn and Curve W1-3,4 – Reverse Turn and Curve W1-5 – Winding Road W1-6,7 – Large Arrow W1-8 – Chevron W1-10 – Intersection in Curve W1-11 – Hairpin Curve W1-15 – 270 Degree Loop W2-1 – Cross Road W2-2,3 – Side Road W2-4,5 – T and Y Intersection W2-6 – Circular Intersection W2-7,8 – Double Side Roads | W1-1,2 – Turn and Curve W1-3,4 – Reverse Turn and Curve W1-5 – Winding Road W1-6,7 – Large Arrow W1-8 – Chevron W1-10 – Intersection in Curve W1-11 – Hairpin Curve W1-15 – 270 Degree Loop W2-1 – Cross Road W2-2,3 – Side Road W2-4,5 – T and Y Intersection W2-6 – Circular Intersection W2-7,8 – Double Side Roads | W3-1 – Stop Ahead W3-2 – Yield Ahead W3-3 – Signal Ahead W4-1 – Merge W4-2 – Lane Ends W4-3 – Added Lane W4-5 – Entering Roadway Merge W4-6 – Entering Roadway Added Lane W6-1,2 – Divided Highway Begins and Ends W6-3 – Two-Way Traffic W10-1,2,3,4,11,12 – Grade Crossing Advance Warning | W3-1 – Stop Ahead W3-2 – Yield Ahead W3-3 – Signal Ahead W4-1 – Merge W4-2 – Lane Ends W4-3 – Added Lane W4-5 – Entering Roadway Merge W4-6 – Entering Roadway Added Lane W6-1,2 – Divided Highway Begins and Ends W6-3 – Two-Way Traffic W10-1,2,3,4,11,12 – Grade Crossing Advance Warning | W11-2 – Pedestrian Crossing W11-3,4,16-22 – Large Animals W11-5 – Farm Equipment W11-6 – Snowmobile Crossing W11-7 – Equestrian Crossing W11-8 – Fire Station W11-10 – Truck Crossing W12-1 – Double Arrow W16-5P,6P,7P – Pointing Arrow Plaques W20-7 – Flagger W21-1 – Worker | W11-2 – Pedestrian Crossing W11-3,4,16-22 – Large Animals W11-5 – Farm Equipment W11-6 – Snowmobile Crossing W11-7 – Equestrian Crossing W11-8 – Fire Station W11-10 – Truck Crossing W12-1 – Double Arrow W16-5P,6P,7P – Pointing Arrow Plaques W20-7 – Flagger W21-1 – Worker | W11-2 – Pedestrian Crossing W11-3,4,16-22 – Large Animals W11-5 – Farm Equipment W11-6 – Snowmobile Crossing W11-7 – Equestrian Crossing W11-8 – Fire Station W11-10 – Truck Crossing W12-1 – Double Arrow W16-5P,6P,7P – Pointing Arrow Plaques W20-7 – Flagger W21-1 – Worker |
| Fine Symbol Signs (symbol signs not listed as bold symbol signs) |||||||
| Special Cases |||||||
| W3-1 – Stop Ahead: Red retroreflectivity ≥ 7 W3-2 – Yield Ahead: Red retroreflectivity ≥ 7; White retroreflectivity ≥ 35 W3-3 – Signal Ahead: Red retroreflectivity ≥ 7; Green retroreflectivity ≥ 7 W3-5 – Speed Reduction: White retroreflectivity ≥ 50 For non-diamond shaped signs, such as W14-3 (No Passing Zone), W4-4P (Cross Traffic Does Not Stop), or W13-1P,2,3,6,7 (Speed Advisory Signs), use the largest sign dimension to determine the proper minimum retroreflectivity level. |||||||
Guidance:
[01] A divided highway crossing should be signed and marked as separate intersections when both of the following conditions are present:
* The paths of opposing left turns from the divided highway cross each other (see Figure 2A-5), and
* There is adequate storage in the interior approaches for the design vehicles expected to cross the divided highway.
[02] If either one or both of the conditions in Paragraph 1 of this Section do not exist, the divided highway crossing should be signed and marked as a single intersection.
Figure 2A-5. Intersection Configuration at a Divided Highway Crossing
Support:
[04] Divided highway crossings with median widths between 30 feet and 85 feet might function as either one or two intersections depending upon the interaction of the opposing left-turn vehicle paths and the available interior storage in the median for a crossing vehicle. Other factors that could determine whether a divided highway crossing is operating as one or two intersections include:
* The geometric design of the divided highway crossing,
* The use of positive offset mainline left-turn lanes,
* The length of the median opening (as measured parallel to the center line of the divided highway),
* The geometric design of the median noses,
* Other roadway geometric considerations such as a skewed side street approach or a variable median width,
* Intersection sight distance,
* The physical characteristics of the design vehicle, and
* The observed prevailing driver behavior with regard to opposing left-turn path interaction.
This work is in the public domain in the United States because it is a work of the United States federal government (see 17 U.S.C. 105).
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