On federal highways, a commercial vehicle can be up to 102 inches wide, which works out to 8.5 feet. That figure is set by federal law and applies across the Interstate Highway System and a broader network of designated federal-aid routes.1Office of the Law Revision Counsel. 49 USC 31113 – Width Limitations It covers tractor-trailers, buses, and most delivery trucks. Passenger cars almost never come close to it, and RVs, farm equipment, and vehicles on smaller roads follow their own rules.
The 102-Inch Commercial Limit
Federal law fixes the commercial vehicle width limit on the National Network at 102 inches. States cannot go higher, and they cannot go lower. The National Network is the entire Interstate system plus qualifying federal-aid highways with lanes designed for at least 12 feet of width.1Office of the Law Revision Counsel. 49 USC 31113 – Width Limitations
Hawaii is the one carve-out. Federal law lets Hawaii keep its own 108-inch maximum for commercial vehicles.2eCFR. 23 CFR 658.15 – Width
What About Cars, SUVs, and Pickups
If you drive a personal vehicle, the 102-inch rule is not something you’ll ever bump into. Compact and midsize cars run roughly 70 to 72 inches wide. Full-size SUVs and the widest pickups top out around 80 to 82 inches. You would need substantial aftermarket work, like extended fender flares or a wide-body kit, before a passenger vehicle got anywhere near the commercial ceiling. Width regulations are aimed at trucks and trailers.
How Vehicle Width Is Measured
The 102 inches is measured from the outside of one side of the vehicle or its load to the outside of the other, whichever is wider. Federal regulations list a range of safety and utility devices that don’t count toward the total.3eCFR. 23 CFR Part 658 – Truck Size and Weight, Route Designations – Length, Width and Weight Limitations – Section 658.16
The exclusions include rear-view mirrors, turn signal lamps, cab handholds, splash and spray suppressants, and load-induced tire bulge. The full list is longer than the commonly cited items. It also covers corner caps, hazardous materials placards, rain gutters, side marker lamps, door hinges, and tarping systems for open-top trailers, provided none of them extends more than three inches from the side of the vehicle.4Legal Information Institute (LII). Appendix D to Part 658 – Devices That Are Excluded From Measurement of the Length or Width of a Commercial Motor Vehicle
That three-inch cutoff is worth paying attention to. An accessory sticking out four inches on each side adds eight inches to the measured width and can push a legal vehicle over the limit. Before adding aftermarket equipment, check whether it qualifies for the exclusion.
Recreational Vehicles
RVs are on a different track. In 2004, the Federal Highway Administration removed recreational vehicles from the definition of a commercial motor vehicle, so the 102-inch federal cap doesn’t apply to them.5Federal Highway Administration. Federal Size Regulations for Commercial Motor Vehicles States regulate RV width directly.
The 2004 change also addressed rolled-up awnings, which can stick out up to six inches from the side of an RV and previously risked triggering an overwidth permit requirement. Under the current rule, states may allow RVs with non-cargo-carrying features extending beyond three inches from the side to operate without a special permit.6Federal Register. Commercial Vehicle Width Exclusive Devices Most Class A motorhomes run between 96 and 102 inches wide, and state rules generally accommodate them. If you’re buying an RV near the 102-inch mark once awnings and slide-outs are counted, check your state’s rules before assuming you’re clear.
Farm Equipment and Special Mobile Vehicles
The federal width limit doesn’t apply to “special mobile equipment” either. That category covers self-propelled vehicles not built primarily to carry people or freight, including farm equipment, road construction machinery, and emergency apparatus.7eCFR. 23 CFR Part 658 – Truck Size and Weight, Route Designations – Length, Width and Weight Limitations – Section 658.5 A combine or a wide tillage implement can easily run 12 or 15 feet across with no federal overwidth permit required.
That doesn’t mean farm equipment can go anywhere at any time. States impose their own restrictions, often limiting travel to daylight and requiring slow-moving vehicle emblems, flashing lights, and other visibility gear. Some states keep farm equipment off the Interstate entirely. The federal exemption removes the width ceiling; state safety rules still govern when and where you can drive.
Local Roads and Restricted Segments
The 102-inch rule is firm on the National Network, but states set their own width limits on roads outside it.8eCFR. 23 CFR Part 658 – Truck Size and Weight, Route Designations – Length, Width and Weight Limitations – Section 658.7 A county road or non-designated state route may carry a tighter limit. A vehicle that’s legal on the Interstate can become overwidth the moment it exits onto a narrower road governed by a lower state cap.
A handful of Interstate segments themselves are restricted below 102 inches. Federal regulations let states impose tighter limits on specific segments where tunnels or bridges have clearance problems. Carriers checking only the headline federal number can miss these; route-specific restrictions matter in tunnels, older urban corridors, and mountain passes.
The one limit on state authority is that local rules cannot deny “reasonable access” to the National Network. A state can restrict a local road to 96 inches, but it cannot use that restriction to effectively cut off commercial vehicles from a nearby Interstate on-ramp.8eCFR. 23 CFR Part 658 – Truck Size and Weight, Route Designations – Length, Width and Weight Limitations – Section 658.7
Oversize Load Permits
When a vehicle or its load is wider than the legal limit, the operator needs a special use permit. Federal law explicitly authorizes states to issue these permits for commercial vehicles wider than 102 inches, including manufactured housing.2eCFR. 23 CFR 658.15 – Width Each state’s department of transportation handles the paperwork, and every state sets its own fees, applications, and conditions.
Single-trip overwidth permit fees vary widely. Some states charge $15 to $20 for a basic trip; others run $60 to $150 or more depending on how much wider the load is and how far it’s traveling. Exceptionally wide loads, sometimes called “superloads,” draw higher fees and closer review. Multi-state routes usually require a separate application in each state, though some states participate in systems that let a single application generate permits for several jurisdictions.9Federal Highway Administration. Best Practices in Permitting Oversize and Overweight Vehicles – Final Report
Permits come with conditions. States typically require prominent “OVERSIZE LOAD” or “WIDE LOAD” signs in black letters on yellow, along with fluorescent flags at the widest points. Sign dimensions, flag sizes, and placement rules are set state by state. Loads above certain widths also require pilot or escort vehicles, and those thresholds and equipment rules are set at the state level as well; the Federal Motor Carrier Safety Administration publishes best-practice guidelines but no binding national standard.10FMCSA. Pilot Car Escort Best Practices Guidelines
Penalties for Going Over Without a Permit
Getting caught overwidth without a permit carries escalating consequences. The first is a fine, which in many states scales with how far over the limit the vehicle is rather than being a flat amount. Officers can also order the vehicle stopped until the violation is fixed, which can mean offloading cargo, rerouting, or waiting for a permit to be issued. For time-sensitive freight, that delay often costs more than the fine.
The bigger exposure is liability. If an overwidth vehicle is in a crash, its non-compliant status becomes a strong factor in the fault analysis, and plaintiff’s attorneys use it as evidence of negligent operation. Insurers may also contest coverage for accidents that happened during an illegal operation. In some states, overwidth violations count as moving violations that put points on a driver’s record, which matters for anyone who drives commercially for a living.