26 CFR §41.4483-6

1. (a)In general. The tax imposed by section 4481 shall be reduced by 25 percent in the case of a truck used in logging.
2. (b)Truck used in logging. The term “truck used in logging” means any highway motor vehicle which—
   1. (1)Is used exclusively during the taxable period for the transportation, to and from a point located on a forested site, of products harvested from such forested site, and
   2. (2)Is registered (under the laws of the State or States in which such vehicle is required to be registered) as a highway motor vehicle used exclusively in the transportation of harvested forest products.