If approaching a railroad crossing while driving a placarded vehicle, you should always:

If approaching a railroad crossing while driving a transit bus, school bus, or placarded vehicle, special procedures apply. Before crossing, stop your vehicle within 50 feet of, but not less than 15 feet from, the nearest rail. Activate your four-way flashers while crossing. Do not stop, change gears, or change lanes while any part of your vehicle is proceeding across the tracks.