What does this sign mean?

• The vehicles bearing this sign are government official vehicles.
• Drivers must slow down but may pass the vehicle with caution.
• Vehicles with this sign are slower than the usual traffic pace.
• Do not pass the vehicle bearing this sign when its lights are flashing.
  Explanation:

  "This road sign informs drivers that they must not pass the vehicle displaying this sign when its lights are flashing. It is typically seen on school buses, emergency vehicles, or other vehicles that may stop frequently or require special caution."