A flag truck is a vehicle that carries warning signs and lights to alert drivers that a slow-moving or oversized load is ahead

Flag trucks are escort vehicles that travel in front of, behind, or alongside wide loads, tall loads, or unusually long loads on public roads. Their job is to warn oncoming traffic that something larger or slower than normal is coming. The truck itself is typically a pickup or medium-duty vehicle equipped with bright flags, flashing lights, and sometimes signs that read "Wide Load" or "Oversized Load."

You'll see flag trucks most often when a company is moving a manufactured home, a large piece of industrial equipment, a boat, or a building component that doesn't fit within standard highway dimensions. Because these loads can't stay within a single lane or travel at normal highway speeds, state law requires that they be escorted by one or more flag trucks to protect other drivers.

Key Takeaways

  • Flag trucks are required by state law when a load exceeds certain width, height, or length limits, which vary by state.
  • The flag truck driver communicates with the load driver by radio and watches for hazards like low bridges, power lines, or narrow road sections.
  • Flag trucks carry warning signs, flashing lights, and sometimes flags to make the oversized load visible from a distance.
  • If you encounter a flag truck and oversized load on the road, slow down and give them extra space, as they cannot maneuver quickly.

When flag trucks are legally required

Each state sets its own rules for when a load is considered oversized and requires a flag truck escort. Generally, a load needs an escort if it exceeds 8.5 feet in width, 13.5 feet in height, or 75 to 85 feet in length — though these thresholds vary by state and sometimes by county or municipality.

The company moving the load must obtain a permit from the state transportation department before the move can happen. The permit specifies which routes are allowed, what time of day the move can occur, and how many flag trucks must accompany the load. Some states require one flag truck; others require two — one in front and one behind.

What flag truck drivers do

A flag truck driver is responsible for spotting hazards that the load driver cannot see from the cab of the main vehicle. This includes low-hanging power lines, tree branches, narrow bridges, or roads that have become too congested for the load to pass safely. The flag truck driver communicates by radio with the load driver and can signal them to stop if an obstacle appears.

Flag truck drivers also manage traffic flow around the oversized load. They may slow down oncoming traffic, warn drivers to stay in their lanes, and watch for vehicles that try to pass unsafely. On highways, they help coordinate with law enforcement if traffic control is needed.

Equipment and markings on a flag truck

A flag truck displays several warning devices so drivers can see it from far away. These typically include bright orange or red flags mounted on the sides or rear, flashing amber or red lights on the roof or bumper, and reflective tape or paint on the vehicle body. Many flag trucks also carry a sign on the back that reads "Oversized Load" or "Wide Load" with arrows pointing to the side where the load extends.

Some flag trucks are equipped with arrow boards — electronic signs that flash directional arrows to guide traffic around the load. Others carry additional lighting or signage depending on the size and nature of the load and the time of day the move occurs.

How to drive safely around a flag truck and oversized load

If you see a flag truck ahead, treat it as a signal to slow down and increase your following distance. Oversized loads travel at reduced speeds — often 35 to 50 miles per hour on highways — and cannot brake or swerve as quickly as a standard vehicle. Do not attempt to pass an oversized load or the flag truck escorting it.

At intersections or on narrow roads, follow the directions of the flag truck driver or any law enforcement officer present. They may hold traffic or direct you into a specific lane to allow the load to pass. Patience at these moments prevents accidents and keeps everyone on the road safer.

The difference between flag trucks and pilot cars

Flag trucks and pilot cars are sometimes used interchangeably, but they serve slightly different purposes. A flag truck is primarily a warning vehicle that alerts other drivers to the presence of an oversized load. A pilot car, by contrast, is often used for extremely large or complex loads and may carry a trained pilot who communicates directly with the load driver and makes real-time decisions about route changes or traffic management.

Some oversized moves use both: a pilot car in front to scout the route and make decisions, and flag trucks behind or alongside to warn traffic. The permit issued by the state determines which type of escort is required for a particular load.

Frequently Asked Questions

Why can't oversized loads just use the highway at night to avoid traffic?

Some moves do occur at night or during off-peak hours, and the permit may specify these times. However, night moves require additional lighting and can be more dangerous for the flag truck driver. Many routes have restrictions on when oversized loads can travel, based on traffic patterns and road conditions.

What happens if a flag truck driver sees a hazard they can't get around?

The flag truck driver radios the load driver to stop. The company may then contact the state transportation department or local authorities to request a temporary road closure, removal of an obstacle, or rerouting. In some cases, the move is delayed until conditions change.

Can I pass a flag truck on a two-lane road?

No. Passing an oversized load or its escort vehicle is illegal and extremely dangerous. The load occupies extra space, the flag truck driver is watching for hazards, and neither vehicle can respond quickly to a passing attempt. Wait until you reach a safe passing zone or a wider road.

Do flag truck drivers need a special license?

Requirements vary by state. Some states require flag truck drivers to hold a commercial driver's license or to complete a training course. Others have fewer formal requirements but expect drivers to understand traffic law and safety procedures. Check your state's transportation department for specific rules.