What vehicles must stop at all railroad crossings?

• Church or school buses, whether or not carrying any passengers at the time of crossing
• Common carriers, such as taxis, buses or other vehicles transporting passengers for hire
• Vehicles transporting flammables, explosives or other dangerous articles as cargo or part of a cargo
• All of the above
  Explanation:

  "The following vehicles are required by law to stop before crossing any railroad grade crossing: 1) Church or school buses, whether or not carrying any passengers at the time of crossing. 2) Common carriers, such as taxis or other vehicles transporting passengers for hire. 3) Vehicles transporting flammables, explosives or other dangerous articles as cargo or part of a cargo."