Delaware Administrative Code
Title 2 - Transportation
2000 - Department of Transportation
2400 - Division of Transportation Solutions
2402 - Manual on Uniform Traffic Control Devices (MUTCD)
Part 2 - Signs
Chapter 2D - GUIDE SIGNS-CONVENTIONAL ROADS
Section 2D.06 - Size of Lettering

01 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. Under optimum conditions, a guide sign message can be read and understood in a brief glance. The legibility distance takes into account factors such as inattention, blocking of view by other vehicles, unfavorable weather, inferior eyesight, or other causes for delayed or slow reading. Where conditions permit, repetition of guide information on successive signs gives the road user more than one opportunity to obtain the information needed.

Standard:

02 Design layouts for conventional road guide signs showing interline spacing, edge spacing, and other specification details shall be as shown in the "Standard Highway Signs and Markings" book (see Section 1A.11).

03 The principal legend on guide signs shall be in letters and numerals at least 6 inches in height for all upper-case letters, or a combination of 6 inches in height for upper-case letters and 4.5 inches in height for lower-case letters. On low-volume roads (as defined in Section 5A.01) with speeds of 25 mph or less, and on urban streets with speeds of 25 mph or less, the principal legend shall be in letters at least 4 inches in height for all upper-case letters, or a combination of 4 inches in height for upper-case letters and 3 inches in height for lower-case letters.

Guidance:

04 Lettering sizes should be consistent on any particular class of highway.

05 The minimum lettering sizes provided in this Manual should be exceeded where conditions indicate a need for greater legibility.