What Is a Flagger?
A flagger is a trained person who controls traffic through or around a work zone, typically using a STOP/SLOW paddle or hand signals. Flaggers stop, slow, and release traffic in coordination with the work. Flagging is common where two directions of traffic must share a single open lane.
Last reviewed: June 24, 2026
Why It Matters
Flaggers are the human point of contact between the work zone and the public, and they stand close to live traffic, so their visibility, position, and signaling are tied directly to safety.
Flagging supports a traffic control plan but does not replace proper advance warning and setup.
Where It Shows Up in the Field
Flaggers are used for one-lane two-way control, at points where vehicles cross the work path, and where real-time control is needed.
A flagger works downstream of advance warning that tells drivers a flagger is ahead, and coordinates with any other flaggers.
Common Mistakes
- Positioning a flagger where drivers cannot see them in time or without an escape path.
- Missing advance warning that a flagger is ahead.
- Using flagging to compensate for an incomplete setup.
What to Check Before Work Begins
- That flagger-ahead advance warning is in place.
- That the flagger has visibility, high-visibility apparel, and an escape path.
- That multiple flaggers coordinate so one lane is not released from both ends.
Related Terms
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Frequently Asked Questions
What does a flagger do?
A flagger controls traffic through or around a work zone by stopping, slowing, and releasing it with a STOP/SLOW paddle or hand signals, coordinating with the work and any other flaggers.
When is a flagger required?
A flagger may be used when traffic needs active, real-time control, such as alternating one-lane traffic. Whether one is required depends on the conditions, the approved plan, and the governing agency.
Need project-specific support?
Work Zone Compliance is an educational resource. Public Ready supports traffic control planning, permit readiness, agency coordination, project-specific sign identification, and equipment sourcing through qualified providers across Southern California.
See Public Ready Services