The Style Guide to America's Highways

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As you drive across America, you'll encounter a wide variety of cultures, landscapes, people, and animals. But the one thing that will stay the same from Maine to California is the signs you pass on the highway. That's because America's roads and highways have a big style guide.

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Traveling across America today, you will encounter a dizzying variety of cultures, landscapes, people and animals. But the one thing that will stay the same from Maine to California is the signs you pass on the highway. And that's because America's roads and highways have a big style guide.

First published in 1935, the Federal Highway Administration's "Manual on Uniform Traffic Control" (MUTCD) is a voluminous volume consisting of nearly 900 pages that contains Federal standards for all traffic safety signs, road markings and other "traffic control devices" that a driver on a highway in the United States might encounter.

The MUTCD states that it "shall be recognized as the national standard for all traffic control devices installed on any street, highway, cycle path or private roadway open to public travel". Exact specifications for font, size, letter spacing, background colors, reflectivity, mounting location, and orientation help ensure signs are always readable at a glance of an eye when driving anywhere in the United States.

Signs warn you of bighorn sheep and direct you to caving. Some examples of MUTCD pages. Source: Federal Highway Administration

The word "uniform" is key here, because you can only imagine the chaos if each state had its own version of stop signs and safety warnings. But states have a certain freedom in the signs they use.

Must, should, can

In its pages, many rules are marked as "Standard" - with the verb "shall", indicating a mandatory or required rule. But some other rules are marked as "Guidance" (the state "should" follow this rule), "Option" (the state "may" follow this rule) or "Support" which simply offers additional information about the rule. The law provides states with flexibility in how they interpret the standards and sets out a process for experimenting with new signs and markers.

By law, each state is required to either adopt the US MUTCD as the standard, supplement the national manual with its own state-specific modifications, or adopt its own manual (as long as it is in "substantial compliance with the national manual"). Ten states have their own MUTCD: California, Texas, Missouri, Minnesota, Utah, Michigan, Indiana, Ohio, Delaware and