The typefaces are defined by the FHWA's Standard Alphabets for Traffic Control Devices, originally published in 1948, and reprinted in 1952.

[2] The lowercase letters, paired with Series E Modified, later became the basis of a national standard for mixed-case legend on freeway guide signs with the 1958 publication of the American Association of State Highway and Transportation Officials (AASHTO) signing and marking manual for Interstate Highways.

Series A has been officially discontinued in the United States due to poor legibility at high speeds, though it continues to be specified for certain signs in New Zealand.

In 2004, the FHWA published lowercase letters for all of the typefaces and made changes to the Manual on Uniform Traffic Control Devices, which allows their use.

[3] The first font only included uppercase letters, with the exception of Series E(M), which was used on large expressway and freeway guide signs.

There was an expectation that over the next few decades, the new Clearview typeface, also specifically developed for use on traffic signs, would replace the FHWA series on some new signage.

[5] In June 2016, a bill challenging this decision was introduced in the United States House of Representatives, which would have ordered the FHWA to reinstate the interim approval for Clearview.

Instead, individuals or companies have developed digital fonts based on the shapes and specifications provided in the standard.

Street name signs usually feature white Series B, C or D letters on a green background, which can be substituted for other colors, such as blue or brown.

On white (regulatory), orange (construction) and yellow (warning) signs, black letters and numbers are used instead.

Frere-Jones made accommodations for smaller print reproduction and Font Bureau released the face under the name Interstate.

In Argentina, new road signs based on the Manual de Señalamiento Vertical—Edición 2017 recently used the FHWA typeface.

In mainland China, newer road signs use the FHWA typeface alongside Helvetica Bold for alphanumeric text.

[14] However, in 2014, Ministry of Transportation passed a regulation to introduce new road signs, being replaced with the new Clearview typeface.

The Netherlands uses a derivative of the FHWA Alphabet Series typeface designed by the ANWB and the Dutch highways and waterways authority.