School zone signs
School Speed Limit When Flashing sign
Sets a lower speed limit that is only mandatory while the attached beacon is flashing, usually during arrival and dismissal times.
- Tall rectangle
- White
- MUTCD S5-1
Shape and background first
Federal designation S5-1 in the MUTCD, the national standard every state signs to. Mounted with a beacon programmed for specific times on school days, sometimes with a digital display instead of fixed amber lights.
What the MUTCD specifies
Designation: S5-1
MUTCD Section 7B.05
Conventional road size: 24 x 48 in
Standard: Use this sign or a school speed limit assembly where a reduced school speed zone is authorized by study or statute.
Source: Federal Highway Administration, MUTCD 11th Edition (December 2023), Part 7, Table 7B-1; Section 7B.05, verified 2026-09-26.
How states handle it
Some states run the beacon on a fixed schedule tied to the school day, while others use radar activated beacons that only flash when a car is actually detected exceeding the school speed limit.
What the test wants you to know
The mistake people make
The speed panel itself stays white and black like any ordinary regulatory sign, it is the separate beacon and often a small plaque above it that carry the fluorescent yellow green color. Exams like to ask what the limit is when the lights are off, and the answer is the regular posted road speed, not the lower school number.
