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Flagging in California: What Flaggers Do and What the Rules Require

A flagger is often the first person a driver meets at a work zone and the only thing standing between moving traffic and the crew. In California, flagging is governed by two sets of rules: Cal/OSHA’s Construction Safety Orders, which protect workers, and Part 6 of the California MUTCD, which sets how traffic control devices and flaggers are used. This page summarizes both.

What a flagger does

Flaggers control traffic where signs and cones alone cannot. Typical jobs include:

  • Alternating traffic through a single open lane on a two-lane road (one-lane, two-way operation)
  • Holding traffic briefly while equipment enters or leaves the road, or while a crane or truck is positioned
  • Slowing traffic past a work area where drivers need extra warning
  • Warning the crew of an approaching vehicle that is not stopping

Cal/OSHA’s rule is direct about when flaggers are needed: under 8 CCR 1599(a), a flagger or flaggers “shall be utilized at locations on a construction site where barricades and warning signs cannot control the moving traffic.” The number of flaggers and how they are deployed follow the California MUTCD.

The CA MUTCD adds that flaggers make the greatest number of contacts with the public of all highway workers, and lists abilities a flagger should be able to demonstrate: communicating clearly and courteously, moving quickly to avoid danger, controlling signaling devices, applying proper traffic control in stressful situations, and recognizing danger in time to warn workers.

Training requirements under Cal/OSHA 1599

Section 1599(g) requires that flaggers be trained in the proper fundamentals of flagging moving traffic before being assigned as flaggers. The training must be based on the CA MUTCD and actual work site conditions, and must include:

  1. Flagger equipment which must be used
  2. Layout of the work zone and flagging station
  3. Methods to signal traffic to stop, proceed or slow down
  4. Methods of one-way traffic control
  5. Trainee demonstration of proper flagging methodology and operations
  6. Emergency vehicles traveling through the work zone
  7. Handling emergency situations
  8. Methods of dealing with hostile drivers
  9. Flagging procedures when a single flagger is used (when applicable)

Training must be documented as required by the employer’s Injury and Illness Prevention Program (8 CCR 3203), and trainers must have the qualifications and experience needed to teach flagging effectively (1599(h)). The CA MUTCD (Section 6D.01) repeats these requirements and refers to Caltrans’ Flagging Instruction Handbook for more detail.

Note that the regulation defines what training must cover rather than naming a specific certificate. Some agencies, project owners or contracts ask for a particular certification card, so check the job’s requirements.

Apparel: what flaggers must wear

  • Daytime: Cal/OSHA 1599(d) requires high-visibility warning garments (vests, jackets or shirts) meeting ANSI/ISEA 107.
  • Night: 1599(e) requires retroreflective garments meeting ANSI/ISEA 107, with retroreflective material visible from at least 1,000 feet, and requires the flagger’s station to be illuminated so the flagger is clearly visible to approaching traffic.
  • Class: the employer selects the apparel class (1599(f)). The CA MUTCD (Section 6C.05) requires Performance Class 2 or 3 apparel for workers in the work zone and recommends Class 3 apparel for flaggers at night.

One detail to be aware of: the Cal/OSHA text still cites the 2004 edition of the ANSI/ISEA 107 standard and the 2012 CA MUTCD, while the CA MUTCD 2026 references ANSI/ISEA 107-2015. In practice, contractors should meet whichever requirement is stricter for the job.

Equipment: the STOP/SLOW paddle and other devices

The CA MUTCD (Section 6D.02) makes the STOP/SLOW paddle the primary and preferred hand-signaling device because it gives drivers more positive guidance than a flag. Key points:

  • The paddle is octagonal on a rigid handle and must be retroreflective at night.
  • Figure 6D-1 shows a minimum size of 18 inches; a 24 x 24 inch paddle may be used where greater emphasis is needed and speeds are 30 mph or more.
  • On a staff, the bottom of the sign should be at least 6 feet above the pavement.
  • Paddles may include white or red flashing lights on the STOP face and white or yellow on the SLOW face, flashing 50 to 60 times per minute.
  • In California, red flags are limited to emergency situations (Section 6D.03). When used, they must be at least 24 inches square on a staff about 36 inches long, and retroreflective at night.
  • A flashlight with a red glow cone may supplement the paddle or flag only in emergency flagging at night at an unlit station (Section 6D.04).

Flaggers may also use an Automated Flagger Assistance Device (AFAD), which lets a flagger control traffic remotely from outside the lane using a STOP/SLOW sign or red and yellow lenses with a gate arm (Sections 6L.02–6L.04).

Section 6D.05 prohibits controlling traffic in a one-lane, two-way operation with hand movements alone, without a paddle, flag or AFAD, except by emergency responders at incident scenes or uniformed law enforcement.

Where flaggers stand

Section 6D.06 and 6D.05 cover flagger stations:

  • Stations must be located so approaching drivers have enough distance to stop at the intended stopping point. The stopping sight distances in Table 6B-2 may be used as a guide, with longer distances on downgrades.
  • Except in emergencies, flagger stations must be preceded by advance warning signs (such as the flagger symbol sign) and must be illuminated when flagging at night.
  • The flagger should stand on the shoulder next to the traffic being controlled, or in the closed lane, and should only step into a moving lane after traffic has stopped.
  • The flagger should be clearly visible to the first approaching driver, stand alone away from other workers and equipment, and identify an escape route.

When flagging is used, and when something else fits better

When two directions of traffic share one lane, the CA MUTCD (Chapter 6E) requires coordinating the movements from each end. Options include flaggers at each end, a single flagger on a short section where both ends are visible, a flag transfer method, a pilot car, temporary traffic signals, or stop or yield control. On a low-volume street with a short work space and clear sight lines, the manual allows traffic to self-regulate.

Flagging tends to fit short-term and intermediate work where traffic must be stopped or alternated. For long-term closures, temporary signals or a detour may be more practical than staffing flaggers around the clock. The choice belongs in the traffic control plan.

Frequently asked questions

Does California require flagger certification?

Cal/OSHA 1599 requires training on specific topics before a worker is assigned to flag, taught by a qualified trainer and documented under the employer’s injury and illness prevention program. It does not name one required certificate, but some agencies and contracts require a specific certification.

What size STOP/SLOW paddle is required in California?

The CA MUTCD shows an 18-inch minimum, with a 24 x 24 inch paddle as an option where more emphasis is needed and speeds are 30 mph or more. The paddle must be retroreflective at night.

Can a flagger use a red flag instead of a paddle?

In California, only in emergency situations. The STOP/SLOW paddle is the standard device.

What vest class does a flagger need?

The CA MUTCD requires ANSI/ISEA 107 Performance Class 2 or 3 apparel in work zones and recommends Class 3 for flaggers at night. The employer is responsible for selecting the class.

How many flaggers are needed?

It depends on the site. Typically one at each end of a one-lane section, with one designated as coordinator; a single flagger can work where the section is short and both ends are visible. The traffic control plan should specify this.

Need a flagging plan?

Safe Pass Traffic prepares traffic control plans, including flagging operations, for projects anywhere in California, with PE & TE stamps available. Your crew or traffic control contractor staffs the flaggers; we design the plan they follow. We’re open 24 hours. Call or text (714) 362-1348 or request a quote.

Related guides

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Sources

This guide is general information based on the sources above, not engineering or legal advice for a specific site. Requirements vary by agency and project.