Guide sign · MUTCD M1-1
Interstate Route Marker
This sign marks a route that is part of the Interstate Highway System. The number tells you which Interstate you are on.
- Shape
- Shield
- Color
- Blue shield with a red top band, white letters and numerals
What to do
Use the number to confirm you are on the route you planned. Even numbers run east-west and odd numbers run north-south, so a wrong parity tells you that you are heading the wrong way. Follow the route markers and green guide signs at interchanges.
Where you see it
Along the highway after each interchange, and on overhead and roadside guide signs.
Test trap
Do not mix it up with the white U.S. route shield or a state route sign: only the Interstate marker is blue and red. Test questions also ask which numbers are north-south (odd) and which are east-west (even).
Memory tip: Red top, blue shield: Interstate. Odd goes north-south, even goes east-west.
Practice question
This sign means:
- A U.S. numbered route
- An Interstate highway route
- A state highway route
- A county road route
Answer: B. The red and blue shield with the legend INTERSTATE marks a route of the Interstate Highway System.
Delaware Driver Manual (July 2026), p. 78