Most general warning signs are diamond-shaped with a black legend and border on a yellow background. School warnings use fluorescent yellow-green, and certain pedestrian, bicycle, and playground warnings may use yellow or fluorescent yellow-green. Temporary traffic-control warnings generally use orange.
At a glance
| Warning group | Common examples | Visual cue |
|---|---|---|
| Alignment | Turns, curves, winding road, chevrons | Yellow diamond with arrow or alignment symbol |
| Intersections | Cross road, side road, T and Y intersections | Yellow diamond with intersection diagram |
| Traffic control ahead | STOP AHEAD, YIELD AHEAD, signal ahead | Yellow diamond with symbol or message |
| Roadway conditions | Merge, lane ends, hill, bump, slippery surface | Yellow diamond |
| Road users and animals | Pedestrian, bicycle, deer, cattle, truck | Yellow or allowed fluorescent background |
| Temporary traffic control | Road work, flagger, lane closure | Typically orange with black legend |
Warning signs depend on the condition
The current MUTCD states that warning-sign use is based on engineering study or engineering judgment. Unnecessary warnings can reduce respect for the sign system, and temporary or seasonal warnings should not remain displayed when their condition is absent.
Plaques add distance, direction, or context
A warning plaque can indicate how far ahead the condition begins, how long it continues, the direction of the condition, or another qualifying message. The plaque and warning sign should be interpreted as a unit.
Finding a warning sign by plain language
Search what you would say naturally—“cow crossing,” “road narrows,” “lane ends,” or “train tracks.” The Sign Finder maps many common phrases to likely W-series designations.
Frequently asked questions
What shape are most warning signs?
Most warning signs are diamond-shaped unless the MUTCD specifies another shape for a particular device.
Are all warning signs yellow?
No. Temporary traffic-control warnings generally use orange, school warnings use fluorescent yellow-green, and certain other warning applications have specific color provisions.
What letter begins warning sign codes?
Most warning sign designations begin with W.