Guide signs
State Route Marker sign
Marks a numbered highway maintained by the state rather than the federal government.
- Square
- White
- MUTCD M1-5
Shape and background first
Federal designation M1-5 in the MUTCD, the national standard every state signs to. The plain square shown here is a stand in for the real thing. Most states design their own outline for this marker, anything from a spade to a keystone to the shape of the state itself.
What the MUTCD specifies
Designation: M1-5
MUTCD Section 2D.11
Conventional road size: 24 x 24 in
Source: Federal Highway Administration, MUTCD 11th Edition (December 2023), Part 2, Table 2D-1, verified 2026-09-26.
How states handle it
Shape and color vary by state since the federal standard only sets a generic square as a fallback, so a driver crossing a state line can watch the route marker change shape even though the road does not change at all.
What the test wants you to know
The mistake people make
The exam rarely asks about the number itself. It asks whether you know a state route can narrow from a divided highway to a single lane county road without warning, so do not assume the same design standards hold along the whole length the way they do on an interstate.
