I Want My 400 Pounds! – Trucking, APUs And Weight Allowances

I Want My 400 Pounds! – Trucking, APUs And Weight Allowances

There’s a lot of hubbub about APUs (Auxiliary Power Units- or generators) these days. Yes, the federal government is allowing up to 400 lbs for trucks with APUs- or any device used to reduce fuel use and emissions. It’s part of the idling reduction strategy- to encourage truckers and trucking companies to install APUs. But that doesn’t mean you can always get it.

The wording of the law says that any vehicle with an APU “may be allowed up to an additional 400 lbs total in gross, axle, tandem, or bridge formula weight limits”- a generator installed on the tractor would not allow for bridge law variance.

The problem is that, though the federal government is allowing the weight increase, the states don’t have to allow it. That means in one state you may be allowed to run up to 80,400 lbs. but in the next state, you may be limited to 80,000 lbs. despite the federal government’s ruling. Many states already have weight tolerances above the 400 lb weight exemption, so the ruling really doesn’t affect the enforcement procedures.

It’s great in theory, but in practice, it’s pretty much worthless.

What we’ve run into is that many officers are unaware of the Federal ruling, so, while a state legislature may have adopted the 400 lb allowance, the enforcement officers may not be aware of it. All of the following information is subject to change and, as always, the right hand may not know what the left hand is doing. Be prepared to show as much documentation as possible whenever you run into a road block!

The following is a list of states and the status of their 400 lb weight exemption status. We are contact state officials directly- none of this is second-hand information. All information is subject to change.

States that have adopted the 400 lb weight allowance (officers at the weigh stations may be unaware):


Arkansas will allow an extra 400 lbs on an axle to account for the APU but will not allow more than 80,000 lbs for gross weight.






Michigan DOES allow 400 lbs for an APU. The problem you may run into is that no weigh station officers we spoke with knew about the Federal ruling and the Michigan Center for Truck Safety was under the impression that Michigan had not adopted the ruling, but could not say for sure. According to Lieutenant Dave Ford, Michigan does indeed honor the 400 lb ruling. Drivers are required to have the APU’s weight documented by the manufacturer and have proof that the documented APU has been installed on that unit (as opposed to a different APU).

North Dakota


Oregon Senate bill 223 officially allows trucks with APU (auxiliary power units) an extra 400 lbs in their gross weight limits. Oregon complies with the federal ruling and requires written certification of the APU’s weight. Oregon motor carrier enforcement officers have been allowing the 400 pound weight exemption since February of 2006. The APU must be in working condition.


The 400 lb weight exemption is allowed on interstate highways only. Drivers on state routes are subject to Virginia’s standard gross and axle weight enforcement.


States that have not adopted the 400 lb weight exemption and:

*have weight tolerances (for scale variance)

*have low fee amounts and won’t make you offload for 400 lbs overweight

*and states whose officers are very unlikely to give you a ticket unless you provoke them- officer discretion is a factor (the officers in many of these states did not know about the 400 lb weight exemption but said the 400 lbs is too low for them to bother with):


Officers at the Greenwich weigh station didn’t know about the Federal ruling, but they said the chances of them writing a citation for such a small amount is unlikely. That stretch of I 95 is limited to 80,000 lbs no matter what permits a driver is carrying, so the limit is 80,000 lbs. 80,001 lbs may result in a ticket, but it’s not likely until the truck reaches 81,000 lbs, depending on officer discretion. The official word from Commercial Vehicle Enforcement Headquarters is that Connecticut has not adopted the 400 pound weight exemption.






Depends entirely on officer discretion- you are not likely to get a ticket for 400 lbs.



New Mexico

New York

North Carolina

Officers at the North Carolina weigh stations that we called didn’t know about the Federal 400 lb allowance but said that they have a 500 lb tolerance that they’ll allow before they start writing tickets.

South Dakota

Officers would not disclose their tolerance allowance but say their tolerance is greater than 400 lbs, so, even though the legilature may not have adopted the Federal standard yet, their current standards allow for the increased weight.


Officers at the Henefer POE say they will allow up to 500 lbs for an APU. Officers at other POEs were unsure about the law.

West Virginia


Officers at the Cheyenne I 25 nb weigh station say they will allow up to 500 lbs over with no ticket.

States that do not allow 400 lbs for an APU (based on our inquiries- subject to change):

Alabama, Arizona, Indiana, New Jersey

There are several states missing from this list. We are still contacting states we have not received an answer from and will provide updated information when it becomes available! Feel free to contact us with your input and experiences.

To get the 400 lb. allowance, you’ll need to be able to provide:

* certified weight of the APU in writing (if your APU only weighs 380 lbs, you’ll only be allowed 380 lbs)

* certified proof (or be able to demonstrate) that the APU is functional (working)

You’ll also want to carry a copy of the Federal regulation with you. You can find it in the Electronic Code of Federal Regulations [http://www.gpoaccess.gov/ECFR/] in Title 23 (Highways), part 658.17 (you’ll find it in section n).