The maximum load height by state is almost always either 13 feet 6 inches or 14 feet, measured from the road surface to the highest point of the vehicle or whatever is strapped on top. There is no federal number. Each state sets its own cap, and anything taller than that cap requires an oversize permit from every state you plan to drive through.
Why the Limit Is Set State by State
The federal government regulates vehicle width and trailer length on major highways, but it has never set a national height limit. The Federal Highway Administration states it directly: “There is no Federal vehicle height requirement for CMVs. Thus, States may set their own height restrictions.”1Federal Highway Administration. Federal Size Regulations for Commercial Motor Vehicles
The reasoning is physical. Width and length affect every road the same way. Height only matters at specific pinch points like bridges, tunnels, and overhead utility lines, and those vary enormously across the country. A number that works for the newer infrastructure out west would be too generous for the older, lower overpasses common in the Northeast and Mid-Atlantic. So the rule-setting was left to the states.
What Most States Allow
Most states cap vehicle and load height at either 13 feet 6 inches or 14 feet on public roads. A few states are more permissive on specific route categories.1Federal Highway Administration. Federal Size Regulations for Commercial Motor Vehicles The variation reflects real differences in infrastructure, with tighter limits in states carrying more old bridges and tunnels.
For a trip that stays within one state, check that state’s department of transportation for the exact figure. For any trip that crosses state lines, check each state you’ll pass through. A load that is perfectly legal where you load it can become a citation the moment you cross a border.
One point worth knowing even if you never leave the Interstate: Interstate highways are built to a 16-foot vertical clearance design standard, which is why commercial trucks running strictly on the Interstate System rarely hit anything overhead.2Federal Highway Administration. Coordination of Vertical Clearance Design Exceptions on the Interstate System Trouble starts when you exit onto state highways, county roads, and city streets.
The State Cap Is Not the Whole Picture
Being under your state’s limit does not mean you can safely drive any road in that state. Individual bridges, tunnels, and overpasses may be posted well below the general cap. A 13-foot-6-inch state limit does nothing for you when a railroad overpass on your route is posted at 11 feet 8 inches.
Bridge strikes by overheight vehicles are a persistent, expensive problem. Most happen not because the driver didn’t know the state limit, but because they didn’t check clearances along their specific route. Passenger-car GPS does not warn about overhead obstacles.
A few habits keep this from happening:
- Pull low-clearance data from each state DOT’s website before you leave.
- Use a routing app built for trucks or RVs, which cross-references your vehicle height against bridge and tunnel databases.
- Stop and measure at any unfamiliar overpass that has no posted clearance. Pilot car operators carry height poles for exactly this reason.3Federal Motor Carrier Safety Administration. Pilot Car Escort Best Practices Guidelines
Posted clearance signs deserve some skepticism. The number on the sign may reflect the original design clearance, and road resurfacing can shave several inches off actual clearance over time. Many experienced haulers subtract 3 to 6 inches from a posted number as a safety margin.
How to Measure Your Vehicle Correctly
Your legal height is measured from a flat, level surface to the absolute highest point of the vehicle or its load, whichever is taller. That single number is what has to come in under the state cap.
The highest point is not always the obvious one. On an RV, it is often a roof-mounted air conditioning unit or antenna. On a flatbed, it is the top of the cargo. On a box truck, it may be the roof of the cargo box itself. Anything bolted, strapped, or stacked on top counts.
Park on level ground and use a telescoping height pole held vertical alongside the vehicle. A tape measure can work but is harder to keep straight on a tall load. Measure at the tallest point, not just the point that’s easy to reach. If the load might shift or settle, measure again after driving a short distance.
When Your Load Is Over the Limit
You can still move an over-height load legally by getting an oversize load permit from every state the route crosses. Each state runs its own program with its own application, fees, and restrictions.
A typical application asks for exact dimensions, gross weight, a detailed proposed route, and travel dates. The permitting agency reviews whether the route can physically accommodate the load without hitting bridges or overhead wires. Most over-height permits cover a single trip on a specified route within a limited window.
Fees for a straightforward single-trip permit generally run between $10 and $50, though exceptionally tall, heavy, or long loads can trigger review fees in the hundreds of dollars. Apply early. Some permits come back in a day; others take weeks if a route survey is required.
Permits typically come with conditions printed on the face of the document: no travel during metro rush hours, no nighttime movement, blackout periods around major holidays, and sometimes weekend restrictions on busy summer corridors. Violating those conditions is treated the same as having no permit at all.
Permitted loads must also be visibly marked. States generally require yellow “OVERSIZE LOAD” banners front and rear, red or orange warning flags on the corners and extremities during daytime travel, and amber and red warning lights for nighttime or low-visibility conditions. Loads above certain thresholds need one or more pilot cars; the escort usually carries its own banner and, for over-height loads, a height pole set to the load’s height to test clearances in advance.3Federal Motor Carrier Safety Administration. Pilot Car Escort Best Practices Guidelines For over-height loads, pilot car requirements often kick in somewhere around 15 to 16 feet, but the exact trigger depends on the state and sometimes the specific route.
What a Violation Costs
Running an over-height load without a permit gets expensive fast, and the ticket is the smallest part of it.
Fines for over-height violations range from a few hundred to several thousand dollars depending on the state, how far over the limit the load is, and whether the violation caused damage. When a bridge strike results in injuries or significant infrastructure damage, drivers have faced criminal charges on top of the traffic citation.
Civil liability is where the real exposure sits. Strike a bridge, overpass, or utility line and the driver and carrier are responsible for all repair costs. Bridge repairs routinely run into the tens or hundreds of thousands of dollars, and if the structure has to close, the economic disruption generates additional claims. Hitting overhead power or communication lines adds utility repair bills and potential liability for downstream outages.
Operational costs stack on top. The vehicle gets held until the height issue is resolved, which may mean rerouting, offloading cargo, or waiting for an escort. For a commercial carrier that downtime is lost revenue, and repeated violations can affect a safety record with federal regulators, making future permits harder to get.