1. (a) Article 21 of the Tax Law specifically excludes certain vehicles from the definition of motor vehicle. Such a vehicle, irrespective of its unloaded or maximum gross weight, is not required to have a permit. The following vehicles if used exclusively for the purposes for which they were designed are excluded:

   1. (1) A vehicle operating on fixed rails or tracks.
   2. (2) A road roller.
   3. (3) A tractor-crane.
   4. (4) A truck-crane.
   5. (5) A power-shovel.
   6. (6) A road building machine.
   7. (7) A snow plow.
   8. (8) A road sweeper.
   9. (9) A sand spreader.
   10. (10) A well driller and
   11. (11) An omnibus except as provided in subdivisions (c) and (d) of this section.

2. (b) The vehicles listed above are excluded from the definition of motor vehicle only when they are used for the purposes for which they were designed. When used for any other purposes they are deemed to be motor vehicles. Accordingly, a permit and plate must be obtained for any vehicle listed above if it is used at any time for any purpose other than that for which it was designed irrespective of the length of time it is so used and if (1) its maximum gross weight is in excess of 18,000 pounds or (2) its unloaded weight is over 4,000 pounds (if a tractor) or over 8,000 pounds (if a truck) and the carrier has elected the unloaded weight method of computing the tax. In such instance its mileage during the period when used for such purpose is subject to tax.

   Example 1:

   A snow plow, which is used for no other purpose, is not a motor vehicle regardless of its maximum gross weight or unloaded weight, and is therefore not required to have a permit.

   Example 2:

   A road building machine, with an unloaded weight of 25,000 pounds, is used for road building operations and is also used in transport materials to customers. It is excluded from the definition of motor vehicle only when used for road building operations. When it is used for any other purpose it is a motor vehicle. Therefore, a permit and plate should be obtained for such motor vehicle. The mileage of the vehicle when it is used as a road building machine is not subject to tax but its mileage when being used for any other purpose is taxable.

3. (c) Any omnibus engaged in the interstate or foreign transportation of passengers and subject to the jurisdiction of the Interstate Commerce Commission, or any agency successor thereto, or one or more State regulatory agencies concerned with the regulation of passenger transport having a seating capacity of more than seven persons in addition to the driver, is considered a motor vehicle for purposes of the additional tax on highway use, the fuel use tax, imposed by section 503-a of the Tax Law and provided for in Article 3 of this Subchapter.
4. (d) An omnibus, irrespective of its unloaded or maximum gross weight, is not required to have a highway use permit and plate for purposes of the truck mileage tax. However, an omnibus engaged in the interstate or foreign transportation of passengers and subject to the jurisdiction of the Interstate Commerce Commission, or any agency successor thereto, or one or more State regulatory agencies concerned with the regulation of passenger transport, having a seating capacity of more than seven persons in addition to the driver, is required to have a permit (form MT-976) and identification sticker (form MT-980) for purposes of the fuel use tax.

Tax Law, § 501, subd. 2; § 503-a, subd. 1, 9