Regulatory signs
Minimum Speed Limit sign
You may not drive slower than the number shown unless weather, traffic or an emergency makes it unsafe to go that fast.
- Tall rectangle
- White
- MUTCD R2-4
Shape and background first
Earlier federal designation R2-4. This artwork is the earlier standalone sign. The current MUTCD uses the R2-4P plaque directly below a maximum speed limit sign; some roads use a combined sign instead.
What the MUTCD specifies
Earlier designation: R2-4
Standard: The current R2-4P minimum speed plaque must be mounted below an R2-1 Speed Limit sign.
This artwork shows the earlier standalone R2-4 sign. The 11th Edition lists the R2-4P plaque instead, and does not give R2-4 a current size.
Source: Federal Highway Administration, MUTCD 11th Edition (December 2023), Part 2, Table 2B-1; Section 2B.24, verified 2026-09-26.
What the test wants you to know
The mistake people make
This is the rare sign that punishes driving too slowly rather than too fast. On a multi-lane freeway, sitting in the left lane below this number is treated the same as a speeding violation in several states.
