What do amber lights on hazard vehicles such as snow plows and tow trucks indicate to other drivers?

• The vehicle is parked and not in use.
• The vehicle is moving at a high speed.
• The vehicle is warning of possible dangers.
  Explanation:

  "Amber lights ​on hazard vehicles such as snow plows and tow trucks, or the combination of amber lights and rear projected blue lights on hazard vehicles designed for towing or pushing disabled vehicles, warn other drivers of possible dangers."
• The vehicle is being towed.