Street Signs

What makes a street name sign legible?


The 2009 MUTCD, ratified on 1/15/2010, made changes to street signs regulations. On 5/04/2012, the FHWA issued a Final Rule that eliminated most compliance set in the 2009 MUTCD, including mandates for street signs.

It is important to understand that elimination of a compliance dates for a given Standard contained in the MUTCD does not eliminate the regulatory requirement to comply with that Standard. The Standard itself remains in the MUTCD and applies to any NEW installations, but the firm fixed date for replacing noncompliant devices has been eliminated.

The wbebsite for the 2009 MUTCD Guide Signs is: For the May 14th, 2012 final rule:

Below are some of the primary D3, street sign, standards that were implemented with the 2009 Federal MUTCD. You need to check with your State regarding ratification of the MUTCD and ancillary State guidelines in place.

Section 2D.43
The lettering for names of streets and highways on Street Name signs shall be composed of a combination of lower-case letters with initial upper-case letters

Lettering on post-mounted Street Name signs (for speeds > 25 mph) should be composed of initial upper-case letters at least 6 inches in height and lower-case letters at least 4.5 inches in height. On multi-lane streets with speed limits greater than 40 mph, the lettering on post-mounted Street Name signs should be composed of initial upper-case letters at least 8 inches in height and lower-case letters at least 6 inches in height. For local roads with speed limits of 25 mph or less, the lettering may be composed of 4" upper-case letters and 3" lower-case letters. Supplementary letters (Rd, St, E, Block #, etc) can be smaller on all signs.

The Street Name sign shall be retroreflective or illuminated to show the same shape and similar color both day and night. The only acceptable background colors for Street Name (D3-1 or D3-1a) signs shall be green, blue, brown, or white. Street signs do not require borders.

FHWA Revision 2 to the 2003 edition of MUTCD December 21, 2007 established minimum levels of retroreflectivity for selected traffic signs, including post mounted street signs. A minimum of Type III sheeting must be used for white/green street signs. 3M High Intensity Prismatic sheeting meets and exceeds those requirements.

In MUTCD Section 2A.08 it states: "Regulatory, warning, and guide signs shall be retroreflective or illuminated to show the same shape and similar color by both day and night, unless specifically stated otherwise in the text discussion in this Manual of a particular sign or group of signs. The requirement for sign illumination shall not be considered to be satisfied by street or highway lighting."

Minimum Maintained Retroreflectivity Levels Street Sign Minimums 

D-3 Minimum Size Plates in the 2009 MUTCD SHS

4" letters,
8" plate

6" letters,
12" plate


Check with your state traffic department for their ratification of the 2009 MUTCD and any ancillary specifications for street signs. You will need to determine what size blades and layouts are appropriate for your agency. Sign legibility is a direct function of letter size and spacing. Legibility distance has to be sufficient to give road users enough time to read and comprehend the sign.

Be aware that blades will typically be larger and they may require upgrades in bracket or installation systems as you use larger letters and subsequently large blades.

 Recommended Minimum Letter Heights on Street Name Signs
 Conventional Road Guide Sign Sizes

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