Fundamentals of Transportation/Traffic Control Devices

Traffic Control Devices include street signs, traffic signals, and road markings. These signs, signals, and stripes guide drivers in navigation and control of their vehicles. Traffic signals are treated above in the section Traffic Signals. Signs and stripings, the other controls, have usage described in the Manual of Uniform Traffic Control Devices (MUTCD).

Road signs in the United States are standardized in the Manual on Uniform Traffic Control Devices, the history of the evolution of this document is given in . Signs evolved from local practice, cities and states copying neighbors, and inventing what they needed, and then later standardizing (first for rural and urban areas separately, and then jointly) after the value of coordination became apparent when automobile travelers crossed jurisdictional boundaries. From the first center line in Michigan in 1911, stop sign in 1915, a 1923 established the basis of the shapes used for road signs today. The Mississippi Valley Association of State Highway Departments proposed the following. Shapes which were most complex to make (circle, octagon) would indicate most danger and be used least often.

• Round: Used to warn of RR crossing;
• Octagon: Used only to signify a stop;
• Diamond: used to indicate ordinary condition of danger requiring precaution at all times;
• Square: Used to indicate intermittent danger conditions requiring little more than ordinary care;
• Rectangular: Used to indicate regulatory or directional information;
• Cut-Out; Used a distinctive shape different from the above to identify highway routes.

This system was improved over time. In 1924 the Minnesota Department of Highways published its Manual of Markers and Signs with the same shapes, but the white background was made yellow. In 1924, the American Association of State Highway Officials adopted the MVASHD plan (with black on yellow), however Red and green on signs rejected because of visibility at night.

Separately, standards were being developed for cities. Traffic signals are largely an urban phenomenon. While the date of the first traffic signal is contested, the electric traffic signal appeared in Cleveland in 1914, and the first three-color traffic signal in 1920. In 1924 the National Conference on Street and Highway Safety developed urban sign recommendations:

• Stop = Red,
• Proceed = Green,
• Caution = Yellow,
• Cross-Roads = Purple or other distinctive color.
• Centerlines = White, but these were to be used only where it was unsafe to be on the left side of the road (curves, hill crests, intersections, railroad crossings)

The objective of AASHO in these early years was first to inventory all of the sign characteristics that had been locally deployed, and then to standardized various aspects: Shape, Word, Color, Symbol, Uniformity of Erection and Application. Even as late as 1930, the third National Conference on Street and Highway Safety, designed for urban published a Manual on Street Traffic Signs, Signals and Markings which had either white or black paint for concrete, and white or yellow paint for bituminous. A red border and legend on yellow was suggested for stop signs.

Finally, in 1932, a Joint Committee on Uniform Traffic Control Devices met to rectify and combine the separate AASHO and NCSHS manuals for rural and urban traffic into a complete manual. Main initial points were color codes, signs at night, and reduced sign sizes in urban areas. Visibility research was undertaken, sponsored by the Bureau of Public Roads. Minor changes continued after this date, though a modern driver would certainly understand the road at this point. For instance, in the 1954 MUTCD the stop sign changes from black on yellow to white on red; yield sign introduced as triangle (black on yellow), emulating European standards.

This table reviews some of the key decisions in the creation of the Manual on Uniform Traffic Control Devices.

Timeline of Traffic Control Devices

• 1911 First center line in Michigan
• 1914 First electric traffic signal installation in Cleveland
• 1915 First stop sign Detroit
• 1920 First three-color traffic signal
• 1923 Shapes agreed to at Mississippi Valley Association of State Highway Departments (Shapes which were most complex to make (circle, octagon) would indicate most danger and be used least often.
• 1924 Minnesota Department of Highways publishes Manual of Markers and Signs (same shapes, white background -> yellow background)
• 1924 AASHO adopts MVASHD (with black on yellow). Red and green on signs rejected because of visibility at night
• 1924 National Conference on Street and Highway Safety developed urban sign recommendations
• 1925: AASHO Manual and Specifications for the Manufacture, Display, and Erection of U.S. Standard Road Markers and Signs ... Tried to build inventory of sign characteristics: Goal of signs: Shape, Word, Color, Symbol, Uniformity of Erection and Application
• 1926 Second National Conference on Street and Highway Safety. Authorized survey from American Engineering Council to collate national practice and make recommendations.
• 1927 Bureau of Public Roads (part of USDA) first national signing manual.
• 1930 Third National Conference on Street and Highway Safety. Publishes Manual on Street Traffic Signs, Signals and Markings. White or black paint for concrete, white or yellow paint for bituminous. Red border and legend on yellow for stop sign. Designed for urban areas.
• 1932 Joint Committee on Uniform Traffic Control Devices met to rectify and combine AASHO and NCSHS separate manuals for rural and urban traffic into a complete manual. Main initial points were color codes, signs at night, and reduced sign sizes in urban areas. Visibility research was undertaken, sponsored by BPR.
• 1935 First Manual on Uniform Traffic Control Devices
• 1942 - War Emergency Edition
• 1948 MUTCD
• 1954 MUTCD - stop sign changes from black on yellow to white on red; yield sign introduced as triangle (black on yellow), emulating European standards.
• 1961 MUTCD
• 1971 MUTCD
• 1978 MUTCD
• 1988 MUTCD
• 2003 MUTCD