75 Pa.C.S. § 4941: Maximum gross weight of vehicles.

(a) General rule.--Except as provided for in subsection (d), no vehicle shall, when operated upon a highway, have a gross weight exceeding 80,000 pounds, and no combination driven upon a highway shall have a gross weight exceeding 80,000 pounds, or the applicable weight set as forth in subsection (b) or (c), whichever is less.

(b) Combination of vehicles.--No combination shall, when operated upon a highway, have a gross weight exceeding the following:

Combination of Vehicles Maximum Gross Weight In Pounds

Two-axle truck tractor & single-axle semitrailer 58,400

Two-axle truck tractor & two-axle semitrailer 73,280

Three-axle truck tractor & single-axle semitrailer 73,280

Two-axle truck & two-axle trailer 73,280

(c) Motor vehicles.--No motor vehicle when operated upon a highway shall have a gross weight exceeding the following specified maximum gross weight for the following described motor vehicles:

Maximum Gross Weight In Pounds

Two-axle motor vehicle 38,000

Three-axle motor vehicle 58,400

Four-axle motor vehicle 73,280

Five-axle motor vehicle 73,280

Six-axle motor vehicle 77,000

Seven-axle motor vehicle 80,000

(d) Natural gas and electric vehicles.--

(1) Notwithstanding any other provision of law, a vehicle that is operated by an engine fueled primarily by compressed or liquefied natural gas or powered primarily by means of electric battery power may exceed the gross vehicle weight limits imposed under this section by an amount, not to exceed a maximum of 2,000 pounds, that is equal to the difference between the weight of the vehicle attributable to the natural gas tank and fueling system or the battery or battery pack carried by the vehicle and the weight of a comparable diesel tank and fueling system.

(2) The weight exemption provided for under this subsection shall apply to all State highways and interstate highways as provided by the exemption permitted under 23 U.S.C. § 127 (relating to vehicle weight limitations-Interstate System).