(a) Except as provided in subsection (f) of this section, the driver of a commercial motor vehicle specified in subsection (b) of this section shall not cross a railroad track or tracks at grade unless he or she first: (1) Stops the commercial motor vehicle within fifty feet of, and not closer than fifteen feet to, the tracks; (2) thereafter, listens and looks in each direction along the tracks for an approaching train; and (3) ascertains that no train is approaching. When it is safe to do so, the driver may drive the commercial motor vehicle across the tracks in a gear that permits the commercial motor vehicle to complete the crossing without a change of gears. The driver shall not shift gears while crossing the tracks.
(b) The following commercial vehicles are required to stop at railroad tracks or tracks at grade:
(1) Every bus transporting passengers;