What does this sign mean?

• Drivers in the bus's lane must stop for the school bus when the signals are flashing.
• Drivers from both directions must stop for the school bus when its signals are flashing.
  Explanation:

  "This sign indicates that drivers from both directions must stop when a school bus has its signals flashing to ensure the safety of children boarding or exiting the bus."
• Drivers in other lanes must come to a complete stop for the school bus when its signals are flashing.
• Drivers from both directions can proceed with caution.