Slippery when wet sign
A yellow diamond with a car leaving two wavy skid marks. It warns of a road surface that can become unexpectedly slippery.
Rules vary by state and country. This explains the sign's standard meaning in the U.S. Manual on Uniform Traffic Control Devices; it isn't legal advice.
How to read it
The MUTCD uses it to warn of unexpected slippery conditions. Pennsylvania's and Michigan's manuals describe the usual case, a surface that becomes especially slippery when wet.
Not only rain
A plaque below the sign can give the reason for the slippery surface. The MUTCD lists legends such as ICE, WHEN WET, STEEL DECK and EXCESS OIL.
More road signs
Sources
- MUTCD 2009 Edition, Chapter 2C: Warning Signs and Object Markers, MUTCD 2009, Part 2, U.S. Federal Highway Administration, Section 2C.32
- Pennsylvania Driver's Manual, Chapter 2: Signals, Signs and Pavement Markings, Pennsylvania Department of Transportation, p. 15
- What Every Driver Must Know, Michigan driver manual, Michigan Department of State, Chapter 5, sign 52
Last reviewed September 25, 2026 by Rory Hansen. How we research