W. Va. Code § 11-24-7a
(b) Motor carriers. -- Motor carriers of property or passengers shall apportion the business income component of their adjusted federal taxable income to this state by the use of the ratio which their total vehicle miles in this state during the taxable year bears to total vehicle miles of the corporation everywhere during the taxable year, except as otherwise provided in this subsection.
(1) Definitions. -- For purposes of this subsection (b):
(2) The provisions of this subsection (b) shall not apply to a motor carrier:
(B) Which neither owns nor rents any real or tangible personal property located in this state, except vehicles, and which makes no more than twelve trips into or through this state during a taxable year.
The mileage traveled under fifty thousand miles or the mileage traveled in this state during the twelve trips into or through this state may not represent more than five percent of the total motor vehicle miles traveled in all states during the taxable year.