Airport Surface Detection Equipment, Model X, or ASDE-X, is a runway

Runway

According to ICAO a runway is a "defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft." Runways may be a man-made surface or a natural surface .- Orientation and dimensions :Runways are named by a number between 01 and 36, which is generally one tenth...

-safety tool that enables air traffic controller

Air traffic controller

Air traffic controllers are the people who expedite and maintain a safe and orderly flow of air traffic in the global air traffic control system. The position of the air traffic controller is one that requires highly specialized skills...

s to detect potential runway conflicts by providing detailed coverage of movement on runways and taxiway

Taxiway

A taxiway is a path on an airport connecting runways with ramps, hangars, terminals and other facilities. They mostly have hard surface such as asphalt or concrete, although smaller airports sometimes use gravel or grass....

s. By collecting data from a variety of sources, ASDE-X is able to track vehicles and aircraft

Aircraft

An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 on airport

Airport

An airport is a location where aircraft such as fixed-wing aircraft, helicopters, and blimps take off and land. Aircraft may be stored or maintained at an airport...

 surfaces and obtain identification information from aircraft transponder

Transponder

In telecommunication, the term transponder has the following meanings:...

s.
Originally the FAA installed 38 ASDE-3A radar systems at the nation's busiest airports.