California Department of Transportation

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Auxiliary Power Units

WHAT IS AN AUXILIARY POWER UNIT?

An auxiliary power unit (APU) is a portable, truck-mounted system that can provide climate control and power for trucks without idling.

WHAT IS THE FEDERAL WEIGHT EXEMPTION?

A 400-pound weight exemption was signed into federal law on August 8, 2005 as part of the Energy Policy Act of 2005.  Section 756 of the Energy Policy Act amended Title 23 United States Code 127(a) to allow an increase in the maximum weight limit on the Interstate System of up to 400 pounds to compensate for the additional weight of APUs installed on any heavy duty vehicle.

For a more information, see these websites:

"National Idling Reduction Network News": A summary of the legislation is on Page 3 of this newsletter, which is sponsored by the U.S. Department of Energy via the University of Chicago and Argonne National Laboratory.

The Energy Policy Act of 2005: See Section 756, "Reduction of Engine Idling," which begins on Page 237. The APU portion is on Page 240.

Title 23, United States Code, Section 127(a)(12)

Title 23, Code of Federal Regulations, Section 658.17(n)

DOES THIS APPLY TO STATE ROUTES?

The Federal Highway Administration (FHWA) published a newsletter dated November 9, 2005 regarding this issue.  The FHWA determined that Section 756 does not preempt state regulations or compel the states to grant the increased weight tolerance.  Section 756 simply prevents the application of the funding sanction to states that choose to allow vehicles operating on the Interstate System to exceed the federal maximum weight limits by 400 pounds for APUs.

WILL CALIFORNIA ALLOW THE 400-POUND APU EXEMPTION?

California Assembly Bill 1772 in the 2009-2010 session would have allowed the 400-pound weight exemption for "idle reduction technology" in California. The bill has been inactive since 2010.

WHAT OTHER STATES ALLOW THE 400-POUND APU EXEMPTION?

A federal survey dated July, 2008, revealed the following results:

22 States allow the 400-pound APU exemption:

Arkansas, Idaho, Indiana, Iowa, Kansas, Maryland, Minnesota, Missouri, Mississippi, Montana, Nevada, New Mexico, New York, North Dakota, Oklahoma, Oregon, South Carolina, South Dakota, Texas, Utah, Washington, and Wisconsin.

11 States do NOT allow the 400-pound APU exemption:

Alabama, California, Colorado, Florida, Georgia, Kentucky, Maine, North Carolina, Ohio, Rhode Island, and Wyoming.

The remaining 17 states are not yet accounted for in the survey.

Note: Caltrans did not verify the information from other states, and is not responsible for its accuracy. To verify this information, you will need to contact each state.


CONTACTS

Caltrans Legal Truck Access Branch
Casey Robb
Manuel Fonseca
General number (916) 654-5741

E-mail: Legal Truck Access Branch.

Return to the Caltrans "Legal Truck Access" page.

Revised 5/14/14.