Runway sensors mounted every 1,000 feet tell the type and amount of precipitation that has accumulated.
Firefighters are on duty around the clock at each airport.
Dumpsters in the terminals gauge their own weight. At nine to 10 tons, they automatically send a signal to the hauling company. Dulles hosts a foreign military installation, the German Military Reservation. A heavy-duty pickup truck leads the way, followed by plows. Snow blowers capable of heaving up to 5,000 tons an hour follow.