Guide & Services Road Sign (M1-1)
Interstate Route Marker (2-Digit) Sign Meaning & Driving Rules
The Interstate Route Marker (MUTCD M1-1) identifies a primary mainline highway in the Dwight D. Eisenhower National System of Interstate and Defense Highways.
Required Driver Action & Right-of-Way Protocol
Use the route number and cardinal direction (NORTH/SOUTH/EAST/WEST) to verify your travel corridor.
Detailed Overview & Purpose
The Interstate Shield uses a red top crown and blue body with white numbers. Interstate numbering follows strict federal rules: One- and two-digit odd-numbered interstates (like I-5, I-95) run North-South (increasing west to east). Even-numbered interstates (like I-10, I-80, I-90) run East-West (increasing south to north).
Key Standard & Origin: Interstate numbering is the exact opposite of US Route numbering: I-5 is on the West Coast and I-95 is on the East Coast, while US 1 is on the East Coast and US 101 is on the West Coast!
Where You'll Find This Sign
Installed on overhead gantries, roadside assemblies, and entrance ramp approaches on all US Interstate freeways.
Common Driver Mistakes to Avoid
Not knowing route numbering orientation (odd = North-South, even = East-West) when planning long-distance trips.
How This Sign Appears on the DMV Knowledge & Road Test
Top DMV exam topic: odd numbers run North-South, even numbers run East-West.
Legal Penalties and Moving Violations
None; guide sign.
Sign Variations & Related Types
3-Digit Interstate (M1-1a)
Designates auxiliary interstate beltways, loops, and spurs.
When you encounter the official Interstate Route Marker (2-Digit) (M1-1) on a roadway, what is your legal duty?
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