At all airports with
air-traffic-control towers, the movement of airside vehicles is coordinated by
controllers who ensure efficient and safe operation through the use of
clearances and
separation standards. With few exceptions (like an aircraft occupying a runway under a "line up and wait" clearance), an active runway is typically used by only one entity at a time. When an unauthorized person or vehicle enters a runway, whether intentional or accidental, the conflict is known as a
runway incursion. Many notable
aviation accidents and incidents have been caused by such a scenario, including the
Tenerife airport disaster, which remains the deadliest airplane accident in history. By the mid-1980s, runway incursion prevention began to attract special attention from aviation authorities, especially in the United States. After several high-profile accidents including
Eastern Airlines 111 and the
1991 Los Angeles airport runway collision, the
National Transportation Safety Board highlighted the need to find new technologies that could address the issue. In 1991, the NTSB issued a formal safety recommendation that the directed the FAA to develop "an alternate, cost effective, system to bring controller and pilot attention to pending runway incursions in time to prevent ground collisions." Development on RWSL began as early as 1992 by
Massachusetts Institute of Technology's Lincoln Laboratory. According to an FAA statement, the system was to include "lights, positioned at the edge of the runway so that they would be visible from aircraft cockpits at the runway entrances, [that] would be activated when sensors notified the system of aircraft on approach or aircraft accelerating and decelerating on the runway." The initial proof-of-concept began in 1992 at Boston's
Logan International Airport with a
model-board driven by algorithms processing inputs from
marine-band radar and the
Automated Radar Terminal System (ARTS). After proceeding with installation of over 170 lights in the real-world environment and collecting data across 8,298 aircraft operations, the system was determined to be feasible and successful at meeting its objectives. During the proof-of-concept, the RWSL achieved over 98% agreement with ATC-issued instructions. In 2010, FAA approved funding to install RWSL at 23 airports from fiscal year 2011 to fiscal year 2016 at a cost of $327 million. ==Components==