26 CFR § 41.4482(c)-1 - Definition of State, taxable period, use, and customarily used.
(b) Taxable period. For the definition of taxable period, see section 4482(c).
(c) Use. The term “use”, as used in the regulations in this part with reference to a highway motor vehicle, means the use of the highway motor vehicle on the public highways in the United States, that is, operation of the vehicle, by means of its own motor, on any roadway (whether a Federal highway, State highway, city street, or otherwise) in the United States which is not a private roadway. Thus, for purposes of the tax, there is no use of a highway motor vehicle while the vehicle is in “dead storage”. The term “use” does not include operation of a new highway motor vehicle on a public highway in the United States if such operation is merely for the purpose of transporting the vehicle from the point of manufacture or assembly to the consumer, whether direct or with intermediate deliveries to such points as are involved in the distribution process. For example, operation of a new vehicle for the purpose of delivering it from the factory to a branch establishment of the manufacturer, or from the factory or branch establishment to a dealer, distributor, or consumer, does not constitute use of the vehicle within the meaning of the regulations in this part; likewise, the further operation of the vehicle by a dealer or distributor for the purpose of delivering the vehicle to a consumer does not constitute use of the vehicle. Similarly, the operation of a secondhand highway motor vehicle by a dealer or distributor for the purpose of delivering the vehicle to a purchaser does not constitute use of the vehicle within the meaning of the regulations in this part. Furthermore, the term “use” does not include operation of a new or secondhand highway motor vehicle, if such operation is exclusively for the purpose of demonstration of the vehicle by a dealer in, or distributor of, new or secondhand highway motor vehicles. Operation of a highway motor vehicle on a private roadway, or other private property, does not constitute use of the vehicle within the meaning of the regulations in this part.
(d) Customarily used. A semitrailer or trailer is treated as customarily used in connection with a highway motor vehicle if the vehicle is equipped to tow the semitrailer or trailer.