A. The minimum overhead clearance above railroad tracks which are used or proposed to be used for transporting freight cars shall be 22 feet, except as otherwise provided in these regulations. Structures constructed before July 28, 1953 may be maintained at existing clearances and additional tracks may be constructed and existing tracks reconstructed under them at the same clearances.
B. The overhead clearance above the top of the rail of tracks located at the entrance and inside of buildings may be reduced to 18 feet provided that:
(1) This clearance applies only to tracks terminating within the building; and
(2) When an overhead clearance of less than 22 feet exists on tracks inside the buildings, all cars, trains, motors, engines, or other equipment shall be brought to a stop before entering the buildings.
C. The clearances provided in this regulation do not apply to the electric wires and equipment required over present and future tracks for the operation of trains by electric energy, provided the carriers concerned promulgate and enforce regulations that prohibit any employee from being on the top of cars while being operated under lower clearances than provided for in this regulation.
D. The clearances provided in this regulation do not apply to engine houses, engine house facilities, tipples, or facilities used for the loading or unloading of bulk commodities.