Va. Code § 46.2-1149.4
The Commissioner, upon written application made by the owner or operator, shall issue an overweight permit for the operation of specialized mobile equipment. Any vehicle operating under a permit issued pursuant to this section shall have a gross weight of no more than 64,000 pounds, a single axle weight of no more than 20,000 pounds, and a tandem axle weight of no more than 44,000 pounds. Such permit shall not designate the route to be traversed nor contain restrictions or conditions not applicable to other vehicles in their general use of the highways. The fee for such permit shall be as provided in § 46.2-1140.1.
For purposes of this section, "specialized mobile equipment" means a self-propelled motor vehicle manufactured for the specific purpose of supporting well-drilling machinery on the job site and whose movement on any highway is incidental to the purpose for which it was designed and manufactured.
Va. Code § 46.2-1149.4