Work zone signs
Utility Work Ahead sign
Crews are repairing or installing power, gas, water, or cable lines on or beside the road. Expect parked utility trucks, open trenches, or a flagger.
- Diamond
- Orange
- MUTCD W21-7
Shape and background first
Federal designation W21-7 in the MUTCD, the national standard every state signs to. Frequently posted on ordinary residential and arterial streets rather than highways, since utility lines run under nearly every road.
What the MUTCD specifies
Designation: W21-7
MUTCD Section 6H.24
Conventional road size: 36 x 36 in
Source: Federal Highway Administration, MUTCD 11th Edition (December 2023), Part 6, Table 6H-1, verified 2026-09-26.
What the test wants you to know
The mistake people make
Unlike a paving job, utility work rarely has a tidy cone taper, so the hazard can appear with almost no notice, a bucket truck half in the lane or a worker stepping out from behind a van. Treat the reduced attention this sign gets as the actual trap the question is testing.
