As airports have grown busier over the years, the potential for collisions on airport runways and taxiways has increased as well. To combat this trend, the FAA has developed ASDE-X, a new runway-safety tool.

ASDE-X enables air traffic controllers to detect potential runway conflicts by providing detailed coverage of movement on runways and taxiways. By collecting data from a variety of sources, ASDE-X is able to track vehicles and aircraft on airport surfaces and obtain identification information from aircraft transponders.

The data that ASDE-X uses comes from a surface-movement radar located on the air traffic control tower or remote tower, multilateration sensors, ADS-B (Automatic Dependent Surveillance-Broadcast) sensors, the terminal automation system, and from aircraft transponders. By fusing the data from these sources, ASDE-X is able to determine the position and identification of aircraft and vehicles on the airport surfaces, as well as of aircraft flying within five miles of the airport. Controllers in the tower see this information presented as a color display of aircraft and vehicle positions overlaid on a map of the airport's runways/taxiways and approach corridors. The system essentially creates a continuously updated map of all airport-surface operations that controllers can use to spot potential collisions.

Consisting largely of off-the-shelf commercial products, ASDE-X is a relatively inexpensive system that will be especially helpful to controllers at night or in bad weather when visibility is poor. Over the next year, the FAA plans to enhance ASDE-X with visual and audio alarms that will alert controllers to possible collisions.

The first ASDE-X was activated for operational use and testing at General Mitchell International Airport in Milwaukee, WI, in June. The system was declared ready for national deployment in October. The FAA plans to deploy ASDE-X to 34 airports over the next four years. Nine of these systems will be installed as enhancements to the older ASDE-3 radars. The full list of airports currently designated to receive ASDE-X is included in an attachment.

In addition to this deployment, the agency also is looking at the possibility of adding ASDE-X technology to the 25 airports that now have ASDE-3 ground radars coupled with the Airport Movement Area Safety System (AMASS). This modification will improve the overall performance of these existing radars by adding multilateration capabilities, and give all 59 of the nation's busiest airports a common surface-surveillance technology.

The ASDE-X system is manufactured by Sensis Corp. of DeWitt, N.Y. A subcontractor to Sensis -- Raytheon of Marlboro, MA -- provides the radar system. The contract is valued at up to $100 million.

1. General Mitchell International Airport (Milwaukee, WI)
2. Orlando International Airport
3. Theodore Francis Green State Airport (Providence, RI )
4. Lambert-St. Louis International Airport
5. Charlotte Douglas International Airport
6. San Jose International Airport
7. San Antonio International Airport
8. William P. Hobby Airport (Houston, TX)
9. Dallas/Ft. Worth International Airport
10. Honolulu International - Hickam AFB Airport
11. Bradley International Airport (Hartford, CT)
12. The William B. Hartsfield Atlanta International Airport
13. Ft. Lauderdale/Hollywood Airport
14. Sacramento International Airport
15. Los Angeles International Airport
16. Raleigh-Durham International Airport
17. Chicago O'Hare International Airport
18. Louisville International Airport-Standiford Field
19. Metropolitan Oakland International Airport
20. Phoenix Sky Harbor International Airport
21. Memphis International Airport
22. Tampa International Airport
23. Indianapolis International Airport
24. Burbank-Glendale-Pasadena Airport
25. Port Columbus International Airport (Columbus, OH)
26. Chicago Midway Airport
27. Colorado Springs Municipal Airport
28. John Wayne - Orange County Airport (Santa Ana, CA)
29. Ontario International Airport (Ontario, CA)
30. Washington Dulles International Airport
31. Austin-Bergstrom International Airport
32. Reno/Tahoe International Airport
33. Albuquerque International Sunport Airport
34. San Juan International Airport

* Four ASDE-X support systems not listed above.