35 ILCS 505/1.16
"Commercial motor vehicle" means a motor vehicle used, designed, or maintained for the transportation of persons or property and either having 2 axles and a gross vehicle weight or registered gross vehicle weight exceeding 26,000 pounds or 11,793 kilograms, or having 3 or more axles regardless of weight, or that is used in combination, when the weight of the combination exceeds 26,000 pounds or 11,793 kilograms gross vehicle weight or registered gross vehicle weight, except for motor vehicles operated by this State or the United States, recreational vehicles, school buses, and commercial motor vehicles operated solely within this State for which all motor fuel is purchased within this State. Vehicles that are exempted from registration, but are required to be registered for operations in other jurisdictions may apply for a motor fuel use tax license and decal under the provisions of the International Fuel Tax Agreement referenced in Section 14a of this Act.
35 ILCS 505/1.16