A pentagon identifies a school-zone warning sign in the United States.
Under the U.S. Manual on Uniform Traffic Control Devices, the distinctive five-sided shape is used for school advance-warning and school-crossing signs. These signs commonly have a fluorescent yellow-green background with black symbols or lettering, making them conspicuous near schools and pedestrian routes.
The pentagonal shape helps drivers recognize a school-related warning even before they can read the symbol or wording. This differs from the diamond shape used for most general U.S. warning signs and from the octagonal shape reserved for STOP signs.
School signs do not by themselves establish one nationwide speed limit. Local authorities set school-zone speed limits and operating times, which must be shown by additional signs or local regulations. Drivers should also watch for crossing guards, children, buses, and changing traffic conditions rather than relying only on the sign’s shape.