The National Committee on Uniform Traffic Control Devices (NCUTCD) advises FHWA on additions, revisions, and changes to the MUTCD.

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.

[4] 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.

"[4] 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] 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.

The single most controversial and heavily debated issue during the early years of the MUTCD was the color of center lines on roads.

[4] This edition settled the long-running debate in favor of white, and also changed the standard color of stop signs from yellow to red.

[4] In 1949, the United Nations Conference on Road and Motor Transport launched a research project to develop a worldwide uniform scheme for highway signs.

France, Chile, Turkey, India, and Southern Rhodesia reciprocated by installing MUTCD signs on their roads.

[10][11] By September 1951, the experts working on the project were in favor of the American proposals for stop signs (at the time, black "STOP" text on a yellow octagon), "cross road", "left or right curve", and "intersection", but were still struggling to reach consensus on symbols for "narrow road", "bumpy or uneven surface", and "steep hill".

[3] Despite the Americans' withdrawal from the research project, the experiments eventually resulted in the Vienna Convention on Road Signs and Signals of 1968.

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.

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),[4][14] and also required that all highway guide signs (not just those on Interstate Highways) contain white text on a green background.

[15] Another major change, inspired by the Vienna Convention,[16] was that 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.

[17] 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.

"[18] Conner was active in the Joint Committee and also represented the United States at international meetings on road traffic safety.

[21] 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.

[25][26] Because the Vienna Convention version was circular, it was given a square backing to conform with the MUTCD shape for regulatory signs, and the words "DO NOT ENTER" were superimposed to ensure American driver comprehension.

[29] The Infrastructure Investment and Jobs Act of 2021 requires the USDOT to update the MUTCD quadrennially,[30] and the eleventh edition was released in 2023.

[31][32] This edition allows painted red bus lanes, rules allowing more crosswalks and traffic signals, new rules for determining speed limits, signage for shoulders that are used part-time as traffic lanes, and new signage for electric vehicle charging stations and autonomous vehicles.

[35][36][37] 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.

[42] The following state-specific MUTCD editions are currently in effect: Federal funding is tied to compliance and serves as an enforcement mechanism for state and local governments.

Apart from the 1971 effort to adopt several Vienna Convention-inspired symbol signs (as explained above), 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.

[3] Warning signs (alerting drivers of unexpected or hazardous conditions) tend to be more verbose than their Vienna Convention counterparts.

[3] 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.

[50] Although it serves a similar role to the 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.

Road signs in Colombia are regulated in the Manual de Señalización Vial standard, which is developed by the Ministry of Transport and based on the United States' MUTCD.

Road signs in Venezuela are regulated in Manual Venezolano de Dispositivos Uniformes para el Control del Tránsito and are based on the United States' MUTCD.