Manual on Uniform Traffic Control Devices

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Manual on Uniform Traffic Control Devices for Streets and Highways
Manual on Uniform Traffic Control Devices, December 2023 cover.png
Cover of the 11th edition
Authors
CountryUnited States
LanguageEnglish
PublishedDecember 19, 2023 (11th edition)
PublisherFederal Highway Administration
Publication date
1935; 89 years ago (1935)
ISBN9781560514732 (2009 edition)
OCLC777002425
Websitemutcd.fhwa.dot.gov

The Manual on Uniform Traffic Control Devices for Streets and Highways (usually referred to as the Manual on Uniform Traffic Control Devices, abbreviated MUTCD) is a document issued by the Federal Highway Administration (FHWA) of the United States Department of Transportation (USDOT) to specify the standards by which traffic signs, road surface markings, and signals are designed, installed, and used. In the United States, all traffic control devices must legally conform to these standards. The manual is used by state and local agencies as well as private construction firms to ensure that the traffic control devices they use conform to the national standard. While some state agencies have developed their own sets of standards, including their own MUTCDs, these must substantially conform to the federal MUTCD.

The MUTCD defines the content and placement of traffic signs, while design specifications are detailed in a companion volume, Standard Highway Signs and Markings. This manual defines the specific dimensions, colors, and fonts of each sign and road marking. The National Committee on Uniform Traffic Control Devices (NCUTCD) advises the FHWA on additions, revisions, and changes to the MUTCD.

The MUTCD is the basis for traffic sign standards throughout the Americas, as an alternative to the Vienna Convention on Road Signs and Signals.[1] First published in 1935, the MUTCD predates the Vienna Convention by over three decades. The MUTCD differs significantly from the European-influenced Vienna Convention, and an attempt to adopt several of the Vienna Convention's standards during the 1970s led to confusion among many US drivers.

History

Early standardization efforts

At the start of the 20th century—the early days of the rural highway—each road was promoted and maintained by automobile clubs of private individuals, who generated revenue through club membership and increased business along cross-country routes. However, each highway had its own set of signage, usually designed to promote the highway rather than to assist in the direction and safety of travelers. In fact, conflicts between these automobile clubs frequently led to multiple sets of signs—sometimes as many as eleven—being erected on the same highway.

Government action to begin resolving the wide variety of signage that had cropped up did not occur until the late 1910s and early 1920s when groups from Indiana, Minnesota, and Wisconsin began surveying existing road signs in order to develop road signage standards. They reported their findings to the Mississippi Valley Association of Highway Departments, which adopted their suggestions in 1922 for the shapes to be used for road signs. These suggestions included the familiar circular railroad crossing sign and octagonal stop sign.[2]

In January 1927, the American Association of State Highway Officials (AASHO) published the Manual and Specifications for the Manufacture, Display, and Erection of U.S. Standard Road Markers and Signs to set standards for traffic control devices used on rural roads.[3] Despite the title, this manual did not have any guidance on pavement markings.[3] In the archaic American English of the 1920s, the term "road marker" was sometimes used to describe traffic control devices which modern speakers would now call "signs."[3] In 1930, the National Conference on Street and Highway Safety (NCSHS) published the Manual on Street Traffic Signs, Signals, and Markings, which set similar standards for urban settings, but also added specific guidance on traffic signals, pavement markings, and safety zones.[3] Although the two manuals were quite similar, both organizations immediately recognized that the existence of two slightly different manuals was unnecessarily awkward, and in 1931 AASHO and NCSHS formed a Joint Committee to develop a uniform standard for both urban streets and rural roads. This standard was the MUTCD.[2]

A national standard

Cover of the first edition of the MUTCD published in 1935

The original edition of the Manual on Uniform Traffic Control Devices for Streets and Highways was published in 1935.[2] Since that time, subsequent editions of the manual have been published with numerous minor updates occurring between, each taking into consideration changes in usage and size of the nation's system of roads as well as improvements in technology.

In 1942, the Joint Committee was expanded to include the Institute of Transportation Engineers, then known as the Institute of Traffic Engineers.[2] The single most controversial and heavily debated issue during the early years of the MUTCD was the color of center lines on roads. The 1948 version of the MUTCD settled the debate in favor of white, and also changed the standard color of stop signs from yellow to red.[3] However, the 1948 MUTCD also allowed for two major exceptions to white center lines: yellow was recommended but not mandatory for double center lines on multi-lane highways and for center lines in no-passing zones.[3]

In 1949, the United Nations Conference on Road and Motor Transport launched a research project to develop a worldwide uniform scheme for highway signs.[2] In 1951, the UN conducted experiments in ten U.S. states to compare the effectiveness of national traffic sign standards from around the world. Signs from six countries were placed along the road for test subjects to gauge their legibility at a distance.[4][5] Test strips were located along Ohio State Route 104 near Columbus,[6] U.S. Route 250 and Virginia State Route 53 near Charlottesville,[7] Minnesota State Highway 101 near Minneapolis,[8] and other roads in New York. France, Chile, Turkey, India, and Southern Rhodesia reciprocated by installing MUTCD signs on their roads.[9] In the U.S., the experiments attracted unexpected controversy and curious onlookers who posed a hazard.[10][11] However, the experiments eventually led to the Vienna Convention on Road Signs and Signals.

In 1953, after cooperating with the UN conference's initial experiments, the United States declined to sign or ratify the UN's then-proposed protocol for a worldwide system of uniform road signs.[2] There were two major reasons behind this decision.[2] First, most U.S. roads and streets were (and still are) under state jurisdiction.[2][9] Second, the United States was developing modern controlled-access highways at the time (culminating in the creation of the Interstate Highway System in 1956), and the novel problems presented by such new high-speed highways required rapid innovations in road signing and marking "that would definitely be impaired by adherence to any international code".[2]

In 1960, the National Joint Committee on Uniform Traffic Control Devices was again reorganized to include representatives of the National Association of Counties and the National League of Cities, then known as the American Municipal Association.[2] In 1961, the MUTCD was again revised to make yellow center lines mandatory for the two exceptions where they had previously been recommended.[3] The 1961 edition was the first edition to provide for uniform signs and barricades to direct traffic around road construction and maintenance operations.[2]

In 1966, Congress passed the Highway Safety Act, Pub. L.Tooltip w:Public Law (United States) 89–564, 72 Stat. 885, which is now codified at 23 U.S.C. § 401 et seq. It required all states to create a highway safety program by December 31, 1968, and to adhere to uniform standards promulgated by the U.S. Department of Transportation as a condition of receiving federal highway-aid funds.[12] The penalty for non-compliance was a 10% reduction in funding. In turn, taking advantage of broad rulemaking powers granted in 23 U.S.C. § 402, the Department simply adopted the entire MUTCD by reference at 23 CFR 655.603. (5 U.S.C. § 552(a)(1), also enacted in 1966, authorizes federal agencies to incorporate by reference technical standards published elsewhere, which means the agency may merely cite the standard and need not republish its entire text as part of the appropriate regulation.) Thus, what was formerly a quasi-official project became an official one. States are allowed to supplement the MUTCD but must remain in "substantial conformance" with the national MUTCD and adopt changes within two years after they are adopted by FHWA.

Late 20th century

Warning signs introduced in the 1971 edition, combining both symbols and words

The 1971 edition of the MUTCD included several significant standards. The MUTCD imposed a consistent color code for road surface markings by requiring all center lines dividing opposing traffic on two-way roads to be always painted in yellow (instead of white, which was to always demarcate lanes moving in the same direction),[3][13] and also required that all highway guide signs (not just those on Interstate Highways) contain white text on a green background.[14] Most of the repainting to the 1971 standard was done between 1971 and 1974, with a deadline of 1978 for the changeover of both the markings and signage.

Further editions were published in 1978 and 1988.[15]

21st century

The Millennium Edition of the MUTCD was published in 2000, followed by another edition in 2003.[15] Both editions provided for optional metric versions of many signs. The 2004 SHS was published in both English and Metric versions.[16]

On January 2, 2008, FHWA published a Notice of Proposed Amendment in the Federal Register containing a proposal for a new edition of the MUTCD, and published the draft content of this new edition on the MUTCD website for public review and comment. Comments were accepted until the end of July 2008.[17] The new edition was published in 2009. Revisions to the 2009 edition were then published in 2022.[18][19]

On December 14, 2020, FHWA published a notice of proposed amendment in the Federal Register containing a proposal for an 11th edition of the MUTCD, publishing the draft content of this new edition online for public review and comment until March 15, 2021.[20] The adoption of the Infrastructure Investment and Jobs Act (IIJA) in November 2021 also directed the USDOT to update the MUTCD by no later than May 15, 2023, and at least every four years thereafter.[21]

On May 15, 2023, despite provisions in the IIJA, the FHWA failed to release a new update to the MUTCD. The FHWA cited volume of comments as a reason for the delay.[22] The 11th edition was released on December 19, 2023, and took effect on January 18, 2024.[23]

Development

Proposed additions and revisions to the MUTCD are recommended to FHWA by the National Committee on Uniform Traffic Control Devices (NCUTCD), a private, non-profit organization. The NCUTCD also recommends interpretations of the MUTCD to other agencies that use the MUTCD, such as state departments of transportation. NCUTCD develops public and professional awareness of the principles of safe traffic control devices and practices and provides a forum for qualified individuals to exchange professional information.

The NCUTCD is supported by twenty-one sponsoring organizations, including transportation and engineering industry groups (such as AASHTO and ASCE), safety organizations (such as the National Safety Council and Advocates for Highway and Auto Safety), and the American Automobile Association. Each sponsoring organization promotes members to serve as voting delegates within the NCUTCD.

Characteristics

Main article: Road signs in the United States

The United States is among the majority of countries around the world that have not ratified the Vienna Convention on Road Signs and Signals (based primarily on European signage traditions), and the FHWA MUTCD differs significantly from the Vienna Convention. Apart from the 1971 effort to adopt several Vienna Convention-inspired symbol signs, achieving worldwide uniformity in traffic control devices was never a priority for AASHTO because the number of motorists driving regularly on multiple continents was relatively small during the 20th century.[2]

Sign categories

The MUTCD assigns an alphanumeric code to most signs. Each code begins with an abbreviation of the sign category:

  • Regulatory signs (R)
  • Warning signs (W), including temporary traffic control zone signs and incident management signs
  • Work zone signs (G)
  • Exit signs (E)
  • Marker signs (M)
  • Destination and distance signs (D)
  • General information signs (I)
  • Recreational and cultural interest area symbol signs (RS)
  • Emergency management and civil defense signs (EM)
  • School signs (S)
  • Object markers (OM)

The MUTCD lacks a mandatory sign group like the Vienna Convention does, a separate category for those signs like "Right Turn Only" and "Keep Right" that tell traffic what it must do instead of what it must not do. Instead, the MUTCD primarily classifies them with the other regulatory signs that inform drivers of traffic regulations.

Symbol signs

A vertical rectangular white sign with a black border, with the words "SPEED LIMIT" above the number "50"
A circular white sign with a red border, with the number "50"
Under the MUTCD, the standard speed limit sign (left) used only in the United States includes the words "speed limit" above the number,[24] while the standard one under the Vienna Convention (right) only requires the number which is used in most countries.[25]

Warning signs (alerting drivers of unexpected or hazardous conditions) tend to be more verbose than their Vienna Convention counterparts.[2] On the other hand, MUTCD guide signs (directing or informing road users of their location or of destinations) tend to be less verbose, since they are optimized for reading at high speeds on freeways and expressways.[2]

Inspired by the 1968 Vienna Convention on Road Signs and Signals,[26] the 1971 MUTCD expressed a preference for a transition to adoption of symbols on signs in lieu of words "as rapidly as public acceptance and other considerations permit."[27] During what was then expected to be a transition period, the MUTCD allowed state highway departments to use optional explanatory word plaques with symbol signs and to continue using the previous standard word message signs in certain cases.[27] Robert Conner, the chief of the traffic control systems division of the Federal Highway Administration during the 1970s, believed that symbol signs were "usually more effective than words in situations where reaction time and comprehension are important."[28] Conner was active in the Joint Committee and also represented the United States at international meetings on road traffic safety.[29]

A diamond-shaped with yellow background and black border, with the words "Draw Bridge"
A diamond-shaped with yellow background and black border, with a symbol of an open draw bridge
The draw bridge warning sign (left) is one of the several signs under the MUTCD that remain text-only, while its equivalent under the Vienna Convention (right) displays a symbol of an open draw bridge

The U.S. adoption of several Vienna Convention-inspired symbol signs during the 1970s was a failure. For example, the lane drop symbol sign was criticized as baffling to U.S. drivers—who saw a "big milk bottle"—and therefore quite dangerous, since by definition it was supposed to be used in situations where drivers were about to run out of road and needed to merge into another lane immediately.[30] American highway safety experts ridiculed it as the "Rain Ahead" sign.[30] Many American motorists were bewildered by the Vienna Convention's symbol sign with two children on it, requiring it to be supplemented with a "School Xing" plaque.[31] The 1971 MUTCD's preference for a rapid transition to symbols over words quietly disappeared in the 1978 MUTCD.[32] The 2000 and 2003 MUTCDs each eliminated a symbol sign that had long been intended to replace a word message sign: "Pavement Ends" (in 2000) and "Narrow Bridge" (in 2003).[33]

Adoption

Map showing state adoption of the 2009 MUTCD:
  Adopted national MUTCD
  Adopted national MUTCD with state supplement
  Adopted state-specific MUTCD

Eighteen states have adopted the national MUTCD as is. Twenty-two states, the District of Columbia, and Puerto Rico have all adopted supplements to the MUTCD.[34][35] Within the federal government, supplements have also been developed by the United States Department of Agriculture's Forest Service,[36] the Department of Defense's Military Surface Deployment and Distribution Command (SDDC)[37][38] and the Department of the Interior's Fish and Wildlife Service[39] and National Park Service.[40] Ten states have adopted their own editions of the MUTCD "in substantial conformance to" an edition of the national MUTCD, annotated throughout with state-specific modifications and clarifications.[34] The Guam Department of Public Works has also adopted the MUTCD in some form.[41]

The following state-specific MUTCD editions are currently in effect as of January 2024:

International influence

The MUTCD has influenced traffic operations standards worldwide.[43] For example, the use of yellow stripes to divide opposing traffic has been widely adopted throughout the Western Hemisphere. Australia, New Zealand, Ireland and some Asian countries use many road signs influenced by the MUTCD.

Australia

Main article: Road signs in Australia

Early Australian road signs followed pre-Worboys designs, as seen in the first Road Signs Code[44] adopted by the Standards Association of Australia (now Standards Australia) in 1935. In 1946, the SAA Road Signs Code replaced these text-heavy signs with symbols against the yellow diamond from the American standard.[45] In 1966, the Australian Committee on Road Devices (ACORD) formed to prepare a successor to the 1960 Road Signs Code. The resulting standard, the Australian Standard Manual of Uniform Traffic Control Devices, was adopted in 1975 by the SAA as AS 1742.[46][47]

Canada

Main article: Road signs in Canada

For road signs in Canada, the Transportation Association of Canada (TAC) publishes its own Manual of Uniform Traffic Control Devices for Canada for use by Canadian jurisdictions.[48] Although it serves a similar role to the FHWA MUTCD, it has been independently developed and has a number of key differences with its US counterpart, most notably the inclusion of bilingual (English/French) signage for jurisdictions such as New Brunswick and Ontario with significant anglophone and francophone population, a heavier reliance on symbols rather than text legends and metric measurements instead of imperial.

The Ministry of Transportation of Ontario (MTO) also has historically used its own MUTCD which bore many similarities to the TAC MUTCDC. However, as of approximately 2000, MTO has been developing the Ontario Traffic Manual (OTM), a series of smaller volumes each covering different aspects of traffic control (e.g., regulatory signs, warning signs, sign design principles, traffic signals, etc.).

Central and South America

During the mid 20th century, many of the countries of Central and South America adopted highway construction and signage standards partly based on the U.S. national MUTCD, as part of an integration project to create a hemisphere-wide Pan-American Highway, which the U.S. intended to counter European influence in the region.[49] In 1954, some Latin American countries adopted the 1952 Protocol on Road Signs and Signals, the United Nations–sponsored precursor to the Vienna Convention on Road Signs and Signals.[50] In June 1958, the Central American Economic Cooperation Committee, an organ of the United Nations Economic Commission for Latin America, approved the Manual of Uniform Highway Signs for Central America (Spanish: Manual de Señales Viales Uniformes para Centroamérica), based on the MUTCD.[51][1]

In December 1971, 11 member states of the Organization of American States adopted the Inter-American Manual on Traffic Control Devices for Streets and Highways (Manual Interamericano de Dispositivos para el Control del Tránsito en Calles y Carreteras), also known as the Agreement of Caracas (Convenio de Caracas), at the Thirteenth Pan American Highway Congress in Caracas, Venezuela.[52] Of the treaty's 11 signatories – Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, the Dominican Republic, Nicaragua, Panama, Uruguay, and Venezuela – only Colombia has ratified it, so it has not entered into force.[53] On May 1991, the OAS member states approved a second edition of the manual at the Sixteenth Pan American Highway Congress in Montevideo, Uruguay.[54]

In December 2000, the Secretariat for Central American Economic Integration, part of the Central American Integration System, published the Central American Manual on Uniform Traffic Control Devices (Manual Centroamericano de Dispositivos Uniformes para el Control del Tránsito) primarily based on the U.S. national MUTCD, the 1958 Manual of Uniform Highway Signs for Central America, and the Inter-American MUTCD. The manual was also influenced by the California Traffic Manual, the UK Traffic Signs Manual, Chile's Manual de Señalización de Tránsito, Mexico's Manual de Dispositivos para el Control de Tránsito en Áreas Urbanas y Suburbanas, Honduras' Manual de Carreteras, and Spain's Normas y señales reguladores de la circulación vial.[55] A second edition of the Central American MUTCD was published in October 2014.[56]

Mexico

Main article: Road signs in Mexico

Mexican road signs incorporate some of the basic sign shapes and colors of the MUTCD, but with a greater emphasis on symbols rather than word legends.[57][58] Some northern Mexican states accommodate American drivers by posting English-language word legends and painting yellow centerline markings according to the MUTCD, while some southwestern U.S. states reciprocate with Spanish-language word legends or symbol signs and measurements in metric units.[59]

Some of the earliest road signs in Mexico were erected by the Automobile Club of Southern California in 1928, prior to standardization efforts in the U.S.[60] In 1957, various entities began implementing the 1952 Protocol on Road Signs and Signals, with slight modifications. However, a lack of national standardization resulted in a mix of U.S.- and U.N.-style signage. In 1965, the Secretariat of Communications and Public Works issued the Manual of Traffic Control Devices (Spanish: Manual de Dispositivos para el Control del Tránsito). Though based on the 1952 protocol, the manual did not make use of all the U.N. symbols; instead, it adopted large portions of the MUTCD by agreement with the Office of Public Roads. A second edition was issued the following year. In 1972, the third edition, retitled the Manual of Traffic Control Devices on Streets and Highways (Manual de Dispositivos para el Control del Tránsito en Calles y Carreterras), incorporated provisions of the Inter-American MUTCD.[61] In the 1990s, a committee responsible for the implementation of the North American Free Trade Agreement found that most signs in Canada, the U.S., and Mexico did not differ by enough to cause a major inconvenience to drivers.[62]

See also

References

  1. ^ a b Durán Ortiz, Mario Roberto (December 2000). "Disposiciones Generales" [General Provisions]. Manual Centroamericano de Dispositivos Uniformes para el Control del Tránsito [Central American Manual on Uniform Traffic Control Devices] (in Spanish) (1st ed.). Guatemala City: Secretariat for Central American Economic Integration. pp. 1.2–1.3.
  2. ^ a b c d e f g h i j k l m n Johnson, A.E. (1965). Johnson, A.E. (ed.). "A Story of Road Signing". American Association of State Highway Officials: A Story of the Beginning, Purposes, Growth, Activities, and Achievements of AASHO. Washington, DC: American Association of State Highway Officials. pp. 129–138.
  3. ^ a b c d e f g h Hawkins, H. Gene; Parham, Angelia H.; Womack, Katie N. (2002). "Appendix A: Evolution of U.S. Pavement Marking System". NCHRP Report 484: Feasibility Study for an All-White Pavement Marking System (PDF). Washington, DC: Transportation Research Board. pp. A-1–A-7. Retrieved August 10, 2020.
  4. ^ Waters, Charles R.; Treble, Gilbert W. (July 1951). "Tests of Highway Signs for United Nations". Traffic Engineering. p. 338.
  5. ^ "Universal Road Signs is U.N. Board Aim". Townsville Daily Bulletin. Townsville, Queensland. September 6, 1952. p. 3 – via Trove.
  6. ^ "Ohioans tell Europe to keep its signs". Mansfield News Journal. United Press. March 27, 1951. p. 11 – via Newspapers.com.
  7. ^ Barnett, David (August 21, 1951). "Foreign Highway Signs Catch Eye". The Richmond News Leader. Richmond, Virginia. p. 1-B – via Newspapers.com.
  8. ^ "U.N. Highway Signs Get Test". Minneapolis Star. March 27, 1951. p. 9 – via Newspapers.com.
  9. ^ a b "U.N. Tests New Road Signs in U.S." Air Bulletin: World Affairs. United States Information Service. 1951. pp. 4–5 – via Google Books.
  10. ^ "Foreign Road Sign Test Arouses Some Criticism". The Independent. Massillon, Ohio. Associated Press. March 27, 1951. p. 12 – via Newspapers.com.
  11. ^ "Road Sign Test for UN Given Up". Daily Press. Newport News, Virginia. Associated Press. March 30, 1951. p. 13 – via Newspapers.com.
  12. ^ Fisher, Edward C. (1961). Vehicle Traffic Law (1967 supp. ed.). Evanston, Illinois: Traffic Institute, Northwestern University. p. 11.
  13. ^ American Association of State Highway Officials; National Joint Committee on Traffic Control Devices (1971). "Section 3B-1, Center Lines". Manual on Uniform Traffic Control Devices for Streets and Highways. Washington, DC: Federal Highway Administration. p. 181. Retrieved July 21, 2020.
  14. ^ American Association of State Highway Officials; National Joint Committee on Traffic Control Devices (1971). "Section 2D-3, Color, Reflectorization, and Illumination". Manual on Uniform Traffic Control Devices for Streets and Highways. Washington, DC: Federal Highway Administration. p. 84. Retrieved July 21, 2020.
  15. ^ a b Manual on Uniform Traffic Control Devices for Streets and Highways (2009 ed.). Washington, D.C.: Federal Highway Administration. July 2022. Table I-1.
  16. ^ Standard Highway Signs 2004 Edition, Metric Version. Washington, D.C.: Federal Highway Administration. 2004. Archived from the original on February 2, 2017.
  17. ^ "Public Comments on new MUTCD". Regulations.gov. docket FHWA-2007-28977.
  18. ^ American Association of State Highway and Transportation Officials; National Joint Committee on Traffic Control Devices (2012). "Change List for Revision Numbers 1 and 2, Dated May 2012, to the 2009 Edition of the MUTCD". Washington, DC: Federal Highway Administration. Retrieved May 9, 2021.
  19. ^ "2009 MUTCD with Revisions 1, 2, and 3, July 2022". Washington, D.C.: Federal Highway Administration. July 2022. Retrieved December 19, 2023.
  20. ^ "National Standards for Traffic Control Devices; the Manual on Uniform Traffic Control Devices for Streets and Highways; Revision". Federal Register. December 14, 2020. Retrieved January 11, 2021.
  21. ^ "Status of Rulemaking for the Eleventh Edition of the MUTCD". Federal Highway Administration. March 2, 2022. Retrieved March 2, 2023.
  22. ^ "Manual on Uniform Traffic Control Devices for Streets and Highways: What's New". Federal Highway Administration. Retrieved 2023-05-15.
  23. ^ 88 FR 87672
  24. ^ "Figure 2B-3. Speed Limit and Photo Enforcement Signs and Plaques". Manual on Uniform Traffic Control Devices for Streets and Highways. Washington, DC: Federal Highway Administration. 2009. Retrieved May 23, 2021.
  25. ^ Vienna Convention on Road Signs and Signals (PDF) (2006 consolidated ed.). Geneva, Switzerland: United Nations Economic Commission for Europe. pp. 41, 91. Retrieved May 23, 2021.
  26. ^ "Symbols to Replace Words on U.S. Traffic Signs". The New York Times. May 31, 1970. p. 58.
  27. ^ a b American Association of State Highway Officials; National Joint Committee on Traffic Control Devices (1971). "Section 2A-13, Symbols". Manual on Uniform Traffic Control Devices for Streets and Highways. Washington, DC: Federal Highway Administration. p. 16. Retrieved July 21, 2020.
  28. ^ Lindsey, Robert (April 23, 1972). "Signs of Progress: Road Symbols Guiding Traffic". The New York Times. p. S22. Retrieved August 19, 2020.
  29. ^ "Robert Conner, Ex-FHA Official, Dies of Cancer". The Washington Post. December 1, 1984.
  30. ^ a b Conniff, James C.G. (March 30, 1975). "Danger: Signs Ahead". The New York Times. p. 183. Retrieved August 19, 2020.
  31. ^ Hazlett, Bill (March 23, 1972). "Some Confusing: Wordless Traffic Signs Popping Up". Los Angeles Times. p. E1.
  32. ^ American Association of State Highway Officials; National Joint Committee on Traffic Control Devices (1978). "Section 2A-13, Symbols". Manual on Uniform Traffic Control Devices for Streets and Highways. Washington, DC: Federal Highway Administration. p. 2A-6.
  33. ^ American Association of State Highway and Transportation Officials; National Joint Committee on Traffic Control Devices (2003). "Introduction". Manual on Uniform Traffic Control Devices for Streets and Highways. Washington, DC: Federal Highway Administration. Retrieved August 26, 2020.
  34. ^ a b "MUTCDs & Traffic Control Devices Information by State". Manual on Uniform Traffic Control Devices. Federal Highway Administration. July 14, 2020. Retrieved July 12, 2021.
  35. ^ Manual de Rotulación para las Vías Públicas en Puerto Rico (PDF) (in Spanish). San Juan, Puerto Rico: Puerto Rico Highways and Transportation Authority. 2020.
  36. ^ Sign and Poster Guidelines for the Forest Service (PDF). Washington, D.C.: United States Forest Service. October 2013. Retrieved November 14, 2023.
  37. ^ Department of Defense Supplement to the National Manual on Uniform Traffic Control Devices for Streets and Highways (PDF). Scott Air Force Base, Illinois: Military Surface Deployment and Distribution Command. 2015.
  38. ^ "MUTCD". Scott Air Force Base, Illinois: Military Surface Deployment and Distribution Command Transportation Engineering Agency. Retrieved November 30, 2021.
  39. ^ Sign Handbook: Signage Policy and Guidance (PDF). Bailey's Crossroads, Virginia: United States Fish and Wildlife Service. June 22, 2022 [March 2019]. Retrieved November 14, 2023.
  40. ^ UniGuide: Identification, Wayfinding and Visitor Information for National Parks (PDF). Washington, D.C.: National Park Service. June 1, 2002.
  41. ^ "List of Approved Requests for Interim Approval". Manual on Uniform Traffic Control Devices. Federal Highway Administration. May 15, 2020. Retrieved January 11, 2021.
  42. ^ "Ohio Supplement to the Manual on Uniform Traffic Control Devices". Columbus, Ohio: Ohio Department of Transportation. January 19, 2024. Retrieved January 19, 2024.
  43. ^ Castro, Candida; Horberry, Tim, eds. (April 14, 2004). The Human Factors of Transport Signs. Boca Raton, Florida: CRC Press. p. 3. ISBN 978-0-203-45741-2 – via Google Books.
  44. ^ Titled in full, the Australian Standard Code for the Design, Location, Erection and Use of Road Traffic Signs and Signals, Known as the SAA Road Signs Code (CE 1-1960).
  45. ^ Donald, Deborah (July 1997). BE WARNED! A review of curve warning signs and curve advisory speeds (Report). Vermont South, Victoria: Australian Road Research Board. p. 1. ISBN 0-86910-740-2. ISSN 0158-0728. ARR 304.
  46. ^ Underwood, Robin (February 2016). A History of Traffic Engineering in Australia (1989 – 2015) (Report). Melbourne: Australian Road Research Board. p. 7. ISBN 978-1-876592-82-0. ISSN 0158-0728. ARR 391.
  47. ^ Standards Australia (2014). Manual of uniform traffic control devices (PDF) (5th ed.). Sydney: [[w:SAI Global|]]. p. 2. AS 1742.1:2014.
  48. ^ "Transportation Association of Canada". Transportation Association of Canada. Retrieved July 14, 2021.
  49. ^ Ficek, Rosa Elena (September 2014). The Pan American Highway: Transformations of a Technology of Integration (PDF). 12th Annual Conference of the International Association for the History of Transport, Traffic and Mobility. Philadelphia: International Association for the History of Transport, Traffic and Mobility. p. 10.
  50. ^ Directorate-General of Technical Services 2023, p. 4.
  51. ^ "General Provisions". Acuerdo Centroamericano sobre señales viales uniformes. Mexico: Central American Economic Cooperation Committee. August 1958. hdl:11362/23631.
  52. ^ "Agreement on the Adoption of the Inter-American Manual on Traffic Control Devices for Streets and Highways". Caracas: Thirteenth Pan American Highway Congress. December 7, 1979.
  53. ^ "Signatories and Ratifications". Washington, D.C.: Organization of American States. Retrieved January 8, 2024.
  54. ^ Manual Interamericano de Dispositivos para el Control del Tránsito en Calles y Carreteras [Inter-American Manual on Traffic Control Devices for Streets and Highways] (PDF) (in Spanish) (2nd ed.). Montevideo: Twenty-First Pan American Highway Congress. May 1991. Prologue.
  55. ^ Durán Ortiz, Mario Roberto (December 2000). "Catálogo de Señales" (PDF). Manual Centroamericano de Dispositivos Uniformes para el Control del Tránsito [Central American Manual on Uniform Traffic Control Devices] (in Spanish) (1st ed.). Guatemala City: Secretariat for Central American Economic Integration.
  56. ^ Manual Centroamericano de Dispositivos Uniformes para el Control del Tránsito [Central American Manual on Uniform Traffic Control Devices] (PDF) (in Spanish) (2nd ed.). Guatemala City: Secretariat for Central American Economic Integration. October 2014. Presentation.
  57. ^ Directorate-General of Technical Services 2023, p. 3.
  58. ^ Hawkins et al. 1996, pp. II-5–II-11.
  59. ^ Hawkins et al. 1996, p. II-12.
  60. ^ Aschmann, Homer (1978). "The Baja California Highway". Brand Book. San Diego: San Diego Corral of the Westerners (5): 168 – via Baja California Information Pages.
  61. ^ Directorate-General of Technical Services 2023, pp. 4–7.
  62. ^ Hawkins et al. 1996, pp. II-12–II-13.

Further reading

External links

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