Runway incursion
A runway incursion is an aviation incident involving improper positioning of vehicles or people on any airport runway or its protected area. When an incursion involves an "active" runway being used by arriving or departing aircraft, the potential for a collision hazard or Instrument Landing System (ILS) interference can exist. At present, various runway safety technologies and processes are commonly employed to reduce the risk and potential consequences of such an event. The internationally-accepted definition of a runway incursion is: In the United States, the FAA classifies runway incursions into 3 types, with 5 levels of severity : The Airport Surface Detection Equipment, Model X (ASDE-X) and the Airport Movement Area Safety System (AMASS) are computerized systems that are intended to alert air traffic controllers to the potential for a runway incursion. Background. Formal study of runway incursions began in the 1980s, following several high-profile near misses and fatal collisions of airliners operating on airport surfaces. One of the earliest reports on the topic was published in 1986 by the American National Transportation Safety Board (NTSB), titled "Runway Incursions at Controlled Airports in the United States". Citing examples like the Tenerife airport disaster and the 1972  Chicago–O'Hare runway collision, a special investigation was opened "to investigate selected runway incursions to determine their underlying causes and to recommend appropriate remedial actions." After detailed examination of 26 incursion incidents occurring in 1985, investigators compiled a list of conclusions and safety recommendations. Among their findings were a need for clearer airport signage, improved controller supervision, and revised training procedures for aircrews and controllers. Despite the valuable data generated by the investigation, the NTSB conceded that, at the time, "the magnitude of the runway incursion problem could not be measured because of both incomplete reporting and follow-up investigations  by the FAA." Two years later in 1988, the Federal Aviation Administration issued its own report, "Reducing Runway Incursions", with the purpose of establishing an integrated program for runway incursion reduction. Its general recommendations included: In January 1991, the FAA published the first edition of its biennial "Runway Incursion Plan" (now known as the "National" "Runway Safety Plan"). The document introduced organizational and legislative reforms alongside new initiatives to leverage research on human factors, design, technological innovation, and professional development. In August 1992, however, a US General Accounting Office (GAO) congressional testimony criticized the agency's budgeting, delayed implementation, and  inadequate reporting of the initiatives, especially its rollout of ASDE-3 radar and Traffic Collision Avoidance System (TCAS) technologies. Despite newfound emphasis on runway incursion prevention, another fatal accident occurred on 30 December, 1990, when eight people were killed after two Northwest Airlines flights collided in fog at Detroit Metropolitan Airport. The NTSB determined the accident's probable cause to be pilot error due to communication errors, inadequate crew resource management (CRM), and disorientation exacerbated by deficient airfield geometry. Additionally, the NTSB recommended stricter airport certification requirements under 14 CFR Part 139 in the areas of lighting and conspicuous markings/signage . In 2000, research into incursions at uncontrolled and non-towered airports was conducted by the Aviation Safety Reporting System based on data gathered by interviewing pilots who had experienced a runway incursion. Interviews lasted around 45 minutes to 1 hour, and the data was de-identified for FAA use in developing safety measures. In 2005, the FAA assisted ICAO in its creation of a formal, internationally-accepted definition of a runway incursion. The new verbiage was first added to the fourteenth edition of "PANS-OPS" "Doc 4444", but it was not until 1 October 2007 that the FAA finally adopted  the ICAO definition. Previously, the FAA had maintained that an incursion only included incidents in which a potential traffic conflict existed. An event without a potential conflict– such as an unauthorized aircraft crossing an "empty" runway– had been defined as a 'surface incident'.