I want my 400 pounds! – Trucks, APUs and weight assignments

There is a lot of fuss about APUs (auxiliary power units or generators) these days. Yes, the federal government allows up to 400 pounds for trucks with APUs or any device used to reduce fuel use and emissions. It’s part of the downtime reduction strategy – encouraging 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 pounds in gross, axle, tandem or bridge formula limits” – a generator installed on the tractor would not allow variations of the bridge law.

The problem is, while the federal government is allowing weight gain, the states don’t have to allow it. That means in one state you can be allowed to run up to 80,400 pounds. but in the next state, you may be capped at 80,000 pounds. despite the ruling of the federal government. Many states already have weight tolerances above the 400-pound weight exemption, so the ruling doesn’t really affect enforcement procedures.

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

What we have found is that many officers are unaware of the federal ruling, so while a state legislature may have adopted the £ 400 allowance, enforcement officers may not be aware. 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 every time you come across a roadblock!

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

States that have adopted the 400-pound weight allowance (officers at weigh stations may not be aware of this):


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






Michigan DOES allow 400 pounds for an APU. The problem you may run into is that no weigh station official we spoke to was aware of the federal ruling and the Michigan Center for Truck Safety was under the impression that Michigan had not adopted the ruling, but not he could say with certainty. According to Lt. Dave Ford, Michigan does comply with the 400-pound rule. The controllers must have the APU weight documented by the manufacturer and have proof that the documented APU has been installed on that drive (as opposed to a different APU).

North Dakota


Oregon Senate Bill 223 officially allows trucks with APUs (Auxiliary Power Units) an additional 400 pounds in their gross weight limits. Oregon complies with the federal rule and requires a written weight certification from the APU. Oregon motor carrier control officials have been allowing the 400-pound weight exemption since February 2006. The APU must be in working order.


The 400-pound weight exemption is allowed only on interstates. Drivers on state routes are subject to Virginia’s standard application of gross and axle weights.


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

* have weight tolerances (for scale variations)

* they have low fee amounts and will not unload for 400 pounds overweight

* and states whose officers are highly unlikely to issue you a fine unless provoked by them – officer discretion is a factor (officers in many of these states did not know about the 400lb weight exemption but said that 400lb is too low for them to bother with):


Greenwich weigh station officials did not know about the federal ruling, but said they are unlikely to write a subpoena for such a small amount. That stretch of I 95 is limited to 80,000 pounds regardless of what permits a driver carries, so the limit is 80,000 pounds. 80,001 pounds can result in a fine, but not likely until the truck reaches 81,000 pounds, at the discretion of the officer. The official word from the Commercial Vehicle Enforcement Headquarters is that Connecticut has not adopted the 400 pound weight exemption.






It is entirely up to the officer’s discretion; you are not likely to be fined 400 pounds.



New Mexico

New York

North Carolina

Officials at the North Carolina weigh stations we called were unaware of the 400-pound federal allocation, but said they have a 500-pound tolerance that they will allow before they start issuing fines.

South Dakota

Officials did not disclose her allowable tolerance, but said her tolerance is greater than 400 pounds, so while the legislature may not yet have adopted the federal standard, its current standards allow for weight gain.


Henefer’s POE officials say they will allow up to £ 500 for an APU. Officers at other points of interest weren’t sure of the law.

West Virginia


Cheyenne I 25 nb weigh station officials say they will allow up to 500 pounds without a penalty.

States that do not allow 400 pounds 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 communicating with states for which we have not received a response and will provide updated information as it becomes available. Feel free to contact us with your comments and experiences.

To get the 400 lb. subsidy, you must be able to provide:

* certified written APU weight (if your APU only weighs 380 pounds, only 380 pounds will be allowed)

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

You will also want to carry a copy of the federal regulation with you. You can find it in the Electronic Code of Federal Regulations [] in Title 23 (Highways), part 658.17 (you will find it in section n).

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