49 U.S.C. § 31701

In this chapter— (1) “commercial motor vehicle”, with respect to— (A) the International Registration Plan, has the same meaning given the term “apportionable vehicle” under the Plan; and (B) the International Fuel Tax Agreement, has the same meaning given the term “qualified motor vehicle” under the Agreement. (2) “fuel use tax” means a tax imposed on or measured by the consumption of fuel in a motor vehicle. (3) “International Fuel Tax Agreement” means the interstate agreement on collecting and distributing fuel use taxes paid by motor carriers, developed under the auspices of the National Governors’ Association. (4) “International Registration Plan” means the interstate agreement on apportioning vehicle registration fees paid by motor carriers, developed by the American Association of Motor Vehicle Administrators. (5) “Regional Fuel Tax Agreement” means the interstate agreement on collecting and distributing fuel use taxes paid by motor carriers in the States of Maine, Vermont, and New Hampshire. (6) “State” means the 48 contiguous States and the District of Columbia.