I don't know if this helps:
067 Pa. Code §Â*175.66.Â* Lighting and electrical systems.
"(l) Auxiliary driving lamps and fog lamps. Auxiliary driving lamps and fog lamps may be installed on a passenger vehicle or light truck if the lamps comply with the following:
(1) Auxiliary driving lamps may not be substituted for headlamps. Auxiliary driving lamps may only be used with high headlamp beams.
(2) Fog lamps may not be substituted for headlamps.
(3) Auxiliary driving lamps and fog lamps shall be mounted on the front, spaced at least 20 inches apart from center to center and at height not more than 42 inches above level surface upon which the vehicle stands nor lower than the lowest chassis part. Rear fog lamps, if originally installed or offered as optional equipment, are acceptable.
(4) Auxiliary driving lamps and fog lamps shall be aimed when the vehicle and lamp assembly are in the straight ahead position with the beam not above horizontal centerline of lamp at 25 feet.
(5) A vehicle specified under this subchapter may have only one pair of approved auxiliary driving lamps and fog lamps.
(6) Auxiliary driving lamps and fog lamps may not be placed in front of a required lamp.
(7) Auxiliary driving lamps may not be used on snowplows as a substitute for headlamps obscured by blade. A substitute for headlamps used on the vehicle shall be complete, approved headlamps having both high and low beams."