Oversize/Overweight Load Permits
The following are the Federally mandated maximum weights for the National System of Interstate and Defense Highways and reasonable access thereto (23 CFR Part 658.17):
Axle spacing is another consideration that must be taken into account when looking at Federal weight compliance. To protect bridges, the number and spacing of axles carrying the vehicle load must be calculated. Thus, a bridge weight formula is also applied to commercial vehicles in determining their compliance with Federal weight limits. The Federal bridge formula applies when the gross weight on two or more consecutive axles exceeds the limitations of the formula, except that two consecutive sets of tandem axles may carry a gross load of 34,000 pounds each if the overall distance between the first and last axle is 36 feet or more.
W=500(LN/N-1 + 12N + 36); where W=overall gross weight on any group of 2 or more consecutive axles to the nearest 500 pounds. L=distance in feet between the extreme of any group of 2 or more consecutive axles, and N=number of axles in the group under consideration
The Federal government does not issue permits for oversize or overweight vehicles. This is a State option.
Permits may be issued by the States without regard to the axle, gross, or Federal bridge formula requirements for nondivisible vehicles or loads. Nondivisible is defined as any load or vehicle exceeding applicable length or weight limits which, if separated into smaller loads or vehicles, would:
Designated divisible load permits may be issued by the State based upon historic State "grandfather" rights or Congressional authorization for a State-specific commodity or route movement at a greater size or weight.
State grandfathered rights regarding longer combination vehicles can be found in Appendix C to 23 CFR Part 658-Trucks Over 80,000 Pounds on the Interstate System and Trucks Over STAA Lengths on the National Network.
States may grant special use permits to motor vehicles, including manufactured housing, that exceed the Federal 102 inch width limitation.
To obtain State permits, you will need to contact the State(s) in which you wish to travel. See below for the State permitting web site, or contact the State permitting office by telephone.
Additional Vehicle Size & Weight Information
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United States Department of Transportation - Federal Highway Administration