Roll-off truck weight limits and the Bridge Formula
Federal law caps gross weight, single axle weight and tandem axle weight on the Interstate System, and then adds a fourth limit that can bind even when the first three are individually legal. On a three-axle roll-off truck the tandem cap usually bites first. What none of these limits can tell you is your own payload, because that depends on facts about your truck we cannot see.
Informational only. Informational only, not legal advice. Federal rules are quoted from the regulations as published; state and local rules sit on top of them and vary. Confirm your own position with the agency named before you rely on it.
Reviewed August 2026
Verify with the agency named in the relevant section above.
The three caps, as published
Federal weight limits on the Interstate System are set by section 127 of title 23 of the United States Code and published by the Federal Highway Administration’s Office of Operations. Three of them are simple numbers.
Read the tandem definition carefully, because it is a spacing test rather than a name. Two axles count as a tandem for this purpose when they are spaced more than 40 inches and not more than 96 inches apart, which makes the measurement, not the axle count, the thing that decides which cap applies.
- Gross vehicle weight: 80,000 pounds.
- Single axle: 20,000 pounds.
- Tandem axles, meaning axles spaced more than 40 inches and not more than 96 inches apart: 34,000 pounds.
The fourth limit, and the one that surprises people
The Bridge Formula is the limit that catches operators who have checked the other three and concluded they are legal. It is written as W = 500[LN/(N-1) + 12N + 36], and it produces a maximum gross weight for any group of consecutive axles on the vehicle.
In that expression, W is the maximum gross weight on the group of consecutive axles being tested, rounded to the nearest 500 pounds. L is the distance in feet between the outer axles of that group. N is the number of axles in the group. The formula is applied to groups, not to the vehicle as a whole, which is why one truck can fail it in one place and pass everywhere else.
The decisive sentence is the one operators skip. Any two or more consecutive axles may not exceed the Bridge Formula weight even when the single axle, tandem axle and gross weights are all individually legal. Passing the three caps above is not a defense against the formula, because the formula is a separate limit rather than a summary of them.
Congress established the formula in 1975 to restrict the weight-to-length ratio of vehicles crossing bridges. Reading it that way makes the shape obvious: the same weight concentrated over a shorter wheelbase is the case the formula exists to restrain, which is precisely the case a short, heavy, densely loaded truck presents.
The statutory exception worth knowing
There is one statutory exception published alongside the formula. Two consecutive sets of tandem axles may each carry 34,000 pounds if the distance between the first and last axles of those tandems is 36 feet or more.
That exception is written for the long combination case rather than for a straight truck, which is a useful thing to notice rather than a reason to skip it. If your fleet grows into tractors and trailers, the exception is part of the arithmetic you inherit along with the equipment.
It also illustrates why the formula cannot be reduced to a single number for the trade. The published limits are a system of interacting rules that consume axle spacing, and axle spacing is a fact about a specific vehicle.
Why the tandem cap usually binds first on a roll-off truck
On a three-axle roll-off truck, the limit that usually binds before the gross limit is the tandem cap. The gross cap of 80,000 pounds is generous relative to what a three-axle straight truck can even be rated for, while the drive tandem is carrying the great majority of a loaded box.
That has a practical consequence for how an operator thinks about a heavy load. The question is rarely whether the whole vehicle is under 80,000 pounds. It is how much of the load has landed on one group of axles, which is a function of where the container sits, how it was loaded, and the truck’s own geometry.
It also explains why weight problems in this trade appear as axle problems on a scale rather than as gross problems. An operator who only checks the gross number is checking the limit least likely to be the one exceeded.
The arithmetic is yours, and so are the inputs
Whether a loaded box puts a particular truck over a legal axle or gross limit depends on that truck’s tare weight, its axle configuration and spacing, and the density of the debris in the can. None of those is a general figure, and this page publishes none of them.
That is deliberate. A page that told you a 30 yard box of mixed construction and demolition debris weighs some specific number would be inventing a density it never measured, and an operator who priced or loaded from that number would be wrong in the direction that costs the most. The regulation gives you the caps. Your truck gives you the rest.
The inputs are all obtainable and none of them require guessing. Tare weight comes from a certified scale with the truck empty. Axle spacing is a measurement. Load weight is a scale ticket. Once you have them, the caps above and the formula above are arithmetic rather than judgment.
We publish the federal caps and the formula. We publish no claim about any particular truck’s legal payload and no debris density, because neither was verified and both would be a guess dressed as a fact.
State permitting sits on top of the federal caps
The limits above are the federal limits on the Interstate System. State oversize and overweight permitting sits on top of them and varies, and this page did not read state weight rules or permit schedules for any state, so it publishes none.
That is not a small gap to route rather than fill. Oversize and overweight permitting is exactly where a heavy trade meets a state agency, and the thresholds, the permit types, the fees and the routing restrictions are all set at that level. The state department of transportation permit office is the place to ask.
One related state layer is worth flagging because it is easy to mistake for a weight limit and is not one. Some states authorize waste transport by registered weight, which is a hauling authorization rather than a road weight cap. It gates whether you may carry the material at all, not how heavy the axle may be.
Where to confirm
The Federal Highway Administration publishes the federal limits and the formula, and its page is the citation below. Your state department of transportation permit office answers the state layer, including anything about non-Interstate highways in that state.
A certified scale answers the questions neither agency can. Nothing on this page is a determination that any particular load is legal or illegal.
What this guide does not settle
Each of these is a thing this page does not answer. They are listed rather than smoothed over, because a gap you can see is worth more than a sentence that reads as though there is none.
- Any particular truck’s legal payload. That depends on tare weight, axle configuration and spacing, and load density, none of which we can see. A certified scale and a tape measure settle it.
- Debris densities for any material or container size. No density figure was verified for this page, so none appears on it.
- State oversize and overweight thresholds, permit types and fees, and what limits a state applies off the Interstate System. Ask the state department of transportation permit office.
Frequently asked questions
How much can a roll-off truck legally haul?
There is no single answer for the trade, because the limits are applied to a specific vehicle. Federal caps on the Interstate System are 80,000 pounds gross, 20,000 pounds on a single axle and 34,000 pounds on a tandem, and the Bridge Formula can bind before any of those. What that leaves for payload depends on your truck’s tare weight and axle spacing.
What is the Bridge Formula and why does it matter?
It is W = 500[LN/(N-1) + 12N + 36], a limit on the gross weight carried by any group of consecutive axles, where L is the distance in feet between the outer axles of the group and N is the number of axles in it. It matters because a group may not exceed it even when the single axle, tandem and gross weights are all individually legal.
Which limit usually stops a three-axle roll-off truck first?
The tandem axle cap of 34,000 pounds usually binds before the 80,000 pound gross cap on a three-axle straight truck, because the drive tandem carries most of a loaded box. That is why weight problems in this trade tend to show up as axle weights rather than gross weights.
Sources, and what each one returned
Every claim above traces to one of these. Where a source is marked as one we could not open, nothing on this page rests on it: it is listed so you can try it yourself, and the note says what our request got back.
Where to go next
The rules are the easy half
Knowing what an agency requires is one thing. Proving, months later, that a box was dropped, swapped and collected on the days you invoiced for is the part that actually costs operators money. SwapProof is being built for that record. It is not open yet — the waitlist is where you hear first.