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What is the MUTCD?

The Manual on Uniform Traffic Control Devices (MUTCD) is a publication of the Federal Highway Administration (FHWA) of the United States Department of Transportation (DOT). It specifies the standards by which traffic control devices, such as road signs, traffic signals, and pavement markings, are designed, installed, and used.

Typically, street and traffic signs that are subjective to MUTCD standards are retro-reflective — meaning they are designed to reflect light back to its source, such as the headlights of a car. These signs are made with materials that reflect light back to the driver and are used to increase visibility in low-light conditions, such as dusk, dawn, or in inclement weather.

Contrarily, illuminated street and traffic signs are internally or externally illuminated by artificial light sources. These signs are more versatile, can be used in more settings, and are visible even in bright, direct sunlight when compared to retro-reflective signage. This makes them an effective solution for meeting the minimum brightness of retro-reflective signs, but with more versatility and better performance. As of January 2023, the MUTCD does not have standards for illuminated signage. Instead, the manual includes guidelines for the design, engineering, placement, and maintenance of them.

What Does MUTCD Say About Illuminated Signage?

The MUTCD’s guidelines for illuminated signage says illuminated signs should enhance the legibility and visibility of signs, especially at night or in low-light conditions. Engineering studies should be conducted to determine if illuminated signs are required and examine factors such as the type and volume of traffic, the speed and characteristics of the roadway, and the distance at which the sign will be viewed. The MUTCD also has guidelines for designing, placing, and maintaining illuminated signs. These guidelines include requirements for the type and intensity of lighting, the color and contrast of the sign face, and the size and spacing of letters and symbols. Following these factors ensures illuminated signs are effective and safe for motorists and pedestrians.

Furthering to help ensure the safety of everyone on the road, there are also sizing guidelines for illuminated MUTCD Traffic Signs.

These specifications state the size of illuminated signs should be based on the character height — the vertical distance from the top of the tallest capital letter or symbol to the bottom of the lowest descender — of the letters or symbols on the sign. Minimum character heights for different types of illuminated MUTCD traffic signs are based on the speed and volume of traffic and the distance at which the sign will be viewed. The MUTCD specifies the following minimum character heights for illuminated signs:

• For freeways and expressways with speeds of 50 mph or higher and for primary arterials with speeds of 45 mph or higher: six inches for the first 500 feet of sign visibility and three inches for each additional 500 feet.
• For other arterials and collectors with speeds of 40 mph or higher: four inches for the first 500 feet of sign visibility and two inches for each additional 500 feet.
• For local streets and driveways with speeds of 25 mph or lower: two inches for the first 50 feet of sign visibility and one inch for each additional 50 feet.

It is important to note that these are minimum character heights. The actual size of illuminated MUTCD traffic signs may need to be larger based on the specific conditions at the location. It is also vital to ensure that the character height is appropriate for the typeface used on the sign. The MUTCD specifies guidelines for selecting typefaces based on legibility, readability, and recognition distance.

Recent Updates to the MUTCD

Periodically (around every five years), the MUTCD is revised to incorporate new technologies, address changing traffic control needs, and reflect current best practices. The current version of the MUTCD is Version 11, published in 2021.

Some of the key differences between MUTCD version 10 and 11 include the following:

• Revised guidelines for the use of roundabouts: MUTCD Version 11 includes updated guidance on the design and operation of roundabouts, including splitter islands, channelizing islands, and pedestrian crossings.
• Revised requirements for pedestrian hybrid beacons: MUTCD Version 11 includes revised guidelines for using pedestrian hybrid beacons, which are traffic control devices used to alert drivers of pedestrians at uncontrolled crosswalks.
• New guidance on using Intelligent Transportation Systems (ITS) technologies: MUTCD Version 11 includes new guidance on using ITS technologies, such as traffic sensors and intelligent traffic signals, to improve traffic flow and safety on streets and highways.
• Revised guidelines for using pavement markings: MUTCD Version 11 includes updated guidance on the design and placement of pavement markings, including using raised pavement markers and inverted channelizing tape.
• New requirements for the use of solar-powered traffic signals: MUTCD Version 11 includes new requirements for the use of solar-powered traffic signals, which are increasingly used in areas where it is difficult to install traditional electrical power systems.

How Does the Updated MUTCD Relate to Illuminated Signs?

Part 5 of Version 11 of the MUTCD is titled “Control of Traffic Through Traffic Control Signals.” It provides guidelines for the design, installation, and operation of traffic control signals and covers an array of topics related to traffic control signals, including:

• The design and placement of traffic control signals, including the use of pole-mounted and overhead signals
• The use of flashing and steady signals, and the meaning of different signal displays
• The use of pedestrian signals and countdown pedestrian signals
• The use of traffic signal preemption and priority systems
• The use of ITS technologies in traffic control signals
• The use of traffic signal warrants, which are criteria used to determine whether a traffic control signal is necessary at a particular location

Regarding MUTCD traffic signs that use light-emitting diodes (LEDs), the MUTCD offers specific guidelines, including:

• LED signs should be designed and installed to ensure they are visible to road users under all lighting conditions, including during daylight, twilight, and at night.
• The intensity of the LED display should be adjusted based on the ambient lighting conditions to ensure that the sign is legible and not excessively bright or distracting to road users.
• The use of flashing or strobing LED displays should be limited to warning signs and other signs intended to attract road users’ attention. The flash rate should not exceed four flashes per second.
• LED signs should use appropriate colors and symbols to convey the intended message. For example, regulatory signs (such as speed limit signs) should use white legends on a green background, while warning signs should use black legends on a yellow background.
• LED signs should be placed sufficiently distanced from the edge of the traveled way to ensure they are visible to road users without causing distraction or glare. The specific placement of LED signs should be determined based on engineering judgment and the specific characteristics of the roadway.

Signal-Tech’s LED traffic signals are manufactured according to the latest MUTCD guidelines, and our build process evolves as the guidelines do. Are you interested in learning more about our MUTCD traffic signs? Contact our knowledgeable sales staff anytime to learn how they can benefit your municipality’s roadways!