1. (a) The maximum gross weight of a tractor for permit purposes is the unloaded weight of the tractor plus the maximum load, to be carried or hauled by it on New York public highways. As indicated above, the maximum gross weight cannot be less than the unloaded weight of the tractor plus the weight of the trailer and the maximum load to be carried by the trailer. The maximum gross weight of a tractor shall not include the weight of a driver and his helper.

2. (b) The maximum gross weight of a tractor-trailer combination for weighing and tax rate purposes is the unloaded weight of the tractor plus the maximum gross weight of the trailer.

   Example:

   If a tractor has an unloaded weight of 12,200 pounds and the heaviest trailer to be hauled by it in New York has a maximum gross weight of 49,800 pounds, the maximum gross weight of the tractor for permit purposes is 62,000 pounds.

Tax Law, § 501, subd. 4