No person shall be required to obtain the registration certificate, license plates, or decals for or pay any registration fee for any self-propelled wheelchair or self-propelled wheelchair conveyance provided it is:

1. Operated by a person who is capable of operating it properly and safely but who, by reason of physical disability, is otherwise unable to move about as a pedestrian; and

2. Not operated on a public highway in this Commonwealth except to the extent necessary to cross the highway.