What is the MUTCD?

Ever wonder why road signs are uniform? The Manual on Uniform Traffic Control Devices is the standard manual issued by the Department of Transportation that provides guidelines for roads in the United States.
Road signage wasn’t a real necessity before the invention of the automobile. In the early 1900s, most long-distance travel was done by train or boat and the automobile was mostly an unreliable curiosity. When Dr. Horatio Nelson Jackson, Sewall Crocker, and Jackson’s bulldog Bud made the first transcontinental road trip in 1903, they drove from San Francisco to New York along mostly dirt roads. At one point in California, Jackson and Crocker were deliberately misdirected 108 miles by a local woman who wanted her family to see a motor car for the first time.
The automobile slowly revolutionized transportation, and car travel grew explosively through the 1920s. Initially, road signs weren’t standardized. Each city and state government adopted its own methods, and long-distance travel routes had signage installed by private auto trail operators, often with commercial motivations. Anyone could put up signage, and competition among auto trails was fierce.
Government action to make road signage uniform began in the 1920s. The Mississippi Valley Association of Highway Departments, made up of the road departments of Indiana, Minnesota, Wisconsin, Michigan, and Ohio, detailed a task force to standardize and modernize road signage, a task which was finished in 1923. Many modern signs, such as the yellow diamond-shaped hazard sign, are directly descended from the Mississippi Valley signs.
In 1927, the American Association of State Highway Officials developed a Rural Sign Manual which established minimum standards for sign design and highway markings. The National Conference on Street and Highway Safety developed a corresponding 1930 manual for urban signage. Realizing that the two standards largely overlapped, the two organizations decided to consolidate their standards, producing the first Manual on Uniform Traffic Control Devices in 1935.
As traffic engineers gained experience, signage gradually reached its modern form. By 1961, signage was recognizably modern: green directional signs, yellow warning signs, red stop signs, and so forth. Orange was added for work zones and temporary regulations in the 1970s, and the center dividing line was changed from white to yellow. Other signs have gradually been added, but on the whole the system has reached a stable, standard form.
1942 MUTCD cover 2000 MUTCD cover Poster produced for the MUTCD’s 80th anniversary, 2015