Warning signs
Road May Flood sign
This stretch is known to flood in heavy rain. Slow down in wet weather and turn back rather than drive into standing water, since you cannot judge its depth from the seat.
- Diamond
- Yellow
- MUTCD W8-18
Shape and background first
Federal designation W8-18 in the MUTCD, the national standard every state signs to. Posted near low lying dips, floodplains and bridges over creeks that are known to overtop their banks during storms.
What the MUTCD specifies
Designation: W8-18
MUTCD Section 2C.34
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.
How states handle it
States with frequent flash flooding, such as Texas and Arizona, back this sign with specific turn around, do not drown laws rather than relying on the sign alone.
What the test wants you to know
The mistake people make
The rule being tested is almost never about the sign itself, it is about what to do at standing water: turn around rather than guess the depth, since a surprising amount of water can float or stall a car and moving water is more dangerous than it looks. Driving through standing water on the assumption the road underneath is intact is the wrong answer every time.
