The federal baseline
On the National Network, four federal figures define a legal load. Anything past one of them is over-dimension somewhere.
- Maximum width
- 8'6"102 inches
- Maximum height
- 13'6"Federal baseline only
- Trailer length
- 53'Semitrailer, National Network
- Gross weight
- 80,000Pounds
Those are the numbers everyone quotes. The trap is treating them as the law in all 48 states, because states set their own limits on state-maintained roads — and they do not agree.
Where your state differs
Height is the clearest example, and the most expensive one to get wrong. A height violation usually means a bridge strike, not a ticket.
| Legal height | States | Notes |
|---|---|---|
| 13'6" | 26 | The figure most drivers quote as universal. It is right in just over half the country. |
| 14'0" | 20 | Legal here, and permitted in the 13'6" states. |
| 14'6" | 2 | Colorado and Nebraska only. |
A 14-foot load is legal in 22 states and needs a permit in 26
If you run 14'0" and plan on the 13'6" rule, you will over-permit half your trips. If you run it and assume 14'0" is fine everywhere, you will be over-height in 26 states. Neither guess is cheap — check the route.
The four dimensions
Width
8'6" is the near-universal legal maximum, and the figure that varies least. It is also the dimension that most often triggers escorts: thresholds commonly start around 12 feet, and frequently differ between two-lane and multilane roads. See the pilot car guide for how that works.
Height
13'6", 14'0" or 14'6" depending on the state, as above. Height also drives survey requirements — several states require certified route inspection above a set height before they will issue at all.
Length
The federal 53' figure applies to the semitrailer on the National Network, not to the whole combination. States regulate overall combination length, trailer length and rear overhang separately, and overhang is the one that catches people out on flatbed loads.
Weight
80,000 lbs gross is the federal ceiling, but axle weights and bridge-formula limits bind long before gross does on many configurations. A load can be under 80,000 lbs and still be overweight on a single axle group.
The divisible-load rule
This is the rule that actually gets drivers cited, because it is not about size at all.
Permits are for non-divisible loads
A divisible load is one that can reasonably be broken into smaller units — pallets, bulk material, multiple pieces of equipment. States will generally not issue an oversize or overweight permit for it; the expectation is that you split the load. Permits exist for cargo that genuinely cannot be reduced: a single piece of machinery, a beam, a tank, a transformer. Getting a permit issued for a load that should have been split does not make the load legal.
Definitions of what counts as reasonable vary, and a few states carve out specific exceptions. If there is any doubt about whether your load qualifies, that is a question to ask before you book the permit — not after you are loaded.
Not sure which of your states you are over in? Send the dimensions and the route. We will tell you exactly which states need a permit — and that answer is free whether or not you order.
Get a quoteWhat it costs to skip it
Running over-dimension without a permit is not a paperwork problem. Depending on the state and the overage, it can mean:
- A fine scaled to how far over legal you are, sometimes per pound over on weight violations
- An immediate out-of-service order — the load stops where it is until it is legal or permitted
- Liability exposure if the load contacts a structure, which insurers examine closely when no permit was in force
- A CSA hit that follows the carrier, not the trip
Set against a permit fee that is usually two figures, the arithmetic is not close.
Questions
What size load needs an oversize permit?
On the National Network the federal baseline is 8'6" wide, 13'6" high, a 53' trailer and 80,000 lbs gross. Exceed any state's limit on any one of those and you need a permit. State limits differ from the federal baseline, so the answer depends on every state you pass through, not just the one you load in.
Is the legal height limit 13'6" everywhere?
No, and this is the most common mistake. 13'6" is the limit in 26 states. Twenty states allow 14'0", and Colorado and Nebraska allow 14'6". A 14'0" load is legal in 22 states and needs a permit in 26.
What is a divisible load?
A load that can reasonably be broken down into smaller units. States will generally not issue an oversize or overweight permit for a divisible load — you are expected to split it. Permits exist for cargo that genuinely cannot be reduced, like a single piece of machinery, a beam or a transformer.
Do I need a permit if only part of my route is over legal?
Yes, for each state where you exceed that state's limits. Permits are issued per state and generally tied to an approved route, so the answer is decided state by state along the whole trip.
Does an oversize permit cover county and city roads?
Usually not. A state permit typically covers state-maintained highways. Where your route uses county or city roads, those jurisdictions may require their own permit.