Warning signs
Slippery When Wet sign
The surface becomes slick in rain or ice. Reduce speed and avoid sudden inputs.
- Diamond
- Yellow
- MUTCD W8-5
How to recognize it
Shape and background first
ShapeDiamonda diamond stood on its point
BackgroundYellowyellow, the warning color
FamilyWarning signsFederal designation W8-5 in the MUTCD.
Federal designation W8-5 in the MUTCD, the national standard every state signs to.
What the MUTCD specifies
Designation: W8-5
MUTCD Section 2C.30
Conventional road size: 30 x 30 in
Source: Federal Highway Administration, MUTCD 11th Edition (December 2023), Part 2, Table 2C-1, verified 2026-09-26.
On the test
What the test wants you to know
The mistake people make
Pavement is most slippery in the first few minutes of rain, when water lifts oil off the surface. That timing detail is a favorite exam question.
Same family
