Work-Zone Signs & Markings
Signs are the language of the work zone. The C-31 exam expects you to read sign color, shape, and code, and to know the rules for message signs.
Color and shape
Orange = temporary traffic control (work zone). Yellow = general warning · red = stop/yield/prohibition · green = guide · blue = motorist services · brown = recreational · fluorescent pink = incident management · fluorescent yellow-green = school/pedestrian. Shapes: octagon = STOP, downward triangle = YIELD, diamond = warning, rectangle = regulatory/guide.
Common work-zone signs
| Code | Legend |
|---|---|
| W20-1 | ROAD WORK AHEAD (usually the first advance sign) |
| W20-4 | ONE LANE ROAD AHEAD |
| W20-5 | RIGHT/LEFT LANE CLOSED AHEAD |
| W20-7 | Flagger (symbol) |
| W3-4 | BE PREPARED TO STOP |
| W21-1 | Workers |
| W4-2 | Lane reduction (lane ends) |
| G20-2 | END ROAD WORK (termination area) |
Nighttime and message signs
Signs used at night must be retroreflective or illuminated — nearby street lighting does not count. Changeable message signs (CMS) follow strict limits: no more than two phases, three lines per phase, legible from at least 750 ft, and never flashing, scrolling, or moving.
Practice: Work-Zone Signs & Markings
Frequently asked
What color are work-zone signs?
What is the difference between the W20-7 and W3-4 signs?
How many phases and lines can a changeable message sign use?
More C-31 Traffic Control topics
Planning & Estimating Traffic Control
C-31 study guide on planning a traffic control zone: the four TTC areas, taper-length formulas, buffer space, advance warning sign spacing, and estimating devices.
Read & practice →Notifications, Permits & Coordination
C-31 study guide on permits and coordination for traffic control work: encroachment permits, 811/USA excavation notice, agency and public notification, and closure windows.
Read & practice →Channelizing Devices & Arrow Boards
C-31 study guide on channelizing devices: cone and drum heights, barricade types, vertical panels, device spacing on tapers and tangents, and arrow board modes.
Read & practice →Flagging Operations
C-31 study guide on flagging: the STOP/SLOW paddle, paddle size, when a flag may be used, flagger signaling methods, and flagger station placement and night lighting.
Read & practice →Transportation & Training
C-31 study guide on transporting traffic control devices and training requirements: flagger training before assignment, what training covers, and where it is documented.
Read & practice →Worker Safety & PPE
C-31 study guide on work-zone worker safety: high-visibility apparel classes, OSHA accident-prevention sign colors, struck-by hazards and the Focus Four, and night-work lighting.
Read & practice →