When is it acceptable to pass a stopped school bus or a passenger vehicle at highway-railway crossings?

• When the crossing has signal lights or gates that are not active
  Explanation:

  "School buses, passenger buses, and trucks carrying hazardous materials must stop at all crossings whether signals are activated. Only pass such stopped vehicles on a multi-lane roadway if the crossing is clearly marked with signal lights and/or gates that are NOT activated."
• When you're in a rush to reach your destination
• When traffic is heavy and passing would ease congestion
• When the stopped vehicle has red flashing lights