Home › CFR › Title 49 › Part 52349 CFR Part 523 — Vehicle Classification§ 523.1— Scope.§ 523.2— Definitions.§ 523.3— Automobile.§ 523.4— Passenger automobile.§ 523.5— Non-passenger automobile.§ 523.6— Heavy-duty vehicle.§ 523.7— Heavy-duty pickup trucks and vans.§ 523.8— Heavy-duty vocational vehicle.§ 523.9— Truck tractors.§ 523.10— Heavy-duty trailers.