Before registering any bus, truck, truck tractor, trailer, or semitrailer, the Administration may require any information and make any investigations or tests necessary to determine whether the vehicle may be operated safely on the highways in compliance with this subtitle. The Administration shall register the vehicle for a maximum permissible gross weight within the limitations set forth in this subtitle. The registration card for each vehicle specified in subsection (a) of this section shall show the gross weight for which the vehicle is registered. If the registered vehicle is a motor vehicle to be used in combination with other vehicles, the registration card also shall show separately the total permissible gross weight of the combination of vehicles. The Administration may issue a special plate that shows the gross weight or weights for which a vehicle or combination of vehicles is registered. If issued, the plate shall be attached to and displayed at all times on the vehicle.