What does a crossbuck sign with a flashing red light indicate on a roadway?

• Drivers must stop completely and proceed only when it is safe.
  Explanation:

  "A crossbuck sign with a flashing red light is used at railroad crossings to alert drivers of an approaching train. The flashing red light requires drivers to come to a full stop, check for approaching trains, and proceed only when it is safe."
• Drivers must slow down and yield to oncoming traffic.
• There's a railroad crossing ahead; proceed without stopping.
• Drivers must stop and wait for a green light.