Warning signs
Reduced Speed Limit Ahead sign
The speed limit is about to drop to the number shown. Begin slowing now so you are already at the new limit by the time you reach it.
- Diamond
- Yellow
- MUTCD W3-5
Shape and background first
Federal designation W3-5 in the MUTCD, the national standard every state signs to. Placed before a drop in speed limit that a driver would not expect, such as approaching a town, a sharp curve or a work zone transition.
What the MUTCD specifies
Designation: W3-5
MUTCD Section 2C.40
Conventional road size: 36 x 36 in
Source: Federal Highway Administration, MUTCD 11th Edition (December 2023), Part 2, Table 2C-1, verified 2026-09-26.
What the test wants you to know
The mistake people make
Unlike the white regulatory speed limit sign, this yellow diamond is only a warning that a lower limit is coming, so the number is not yet the law at the sign itself. The new limit only becomes enforceable once you pass the white regulatory sign that follows, and that distinction is exactly what test writers like to probe.
The sign people confuse it with
Reduced Speed Limit Ahead gets mixed up with Speed Limit more than any other pairing in this category. Put them side by side and the difference is obvious, which is exactly why it is worth doing once rather than meeting them cold in the exam.
Reduced Speed Limit Ahead
The speed limit is about to drop to the number shown.
Speed Limit
The maximum legal speed in ideal conditions on this stretch of road.
