4.0   Runway Safety Performance
This section provides a summary description of the metrics used to assess runway safety performance and the results for the period covered by FY 2004 through FY 2007. A much more detailed discussion is available in the 2008 Runway Safety Report. Airports in the United States with FAA-sponsored airport traffic control towers must report operational surface incidents, which may take place on the runway environment or on other airport movement areas. The FAA reviews all of these incidents and identifies a subset as runway incursions.

4.1  Performance Metrics
The FAA uses three primary metrics to assess runway incursions: the frequency of runway incursions, the severity of runway incursions and the types of runway incursions. We use these metrics herein to examine national trends. The Glossary in Appendix B contains detailed definitions for severity categories A through D and runway incursion types.
Frequency of Runway Incursions
The FAA describes both the number and rate of runway incursions to accurately determine runway safety trends. The number of incursions provides a description of magnitude. The rate is how often events occur for a given number of operations. Because the rate accounts for the different number of operations at each airport, it serves as a basis for comparing runway safety trends among airports.
Severity of Runway Incursions
The FAA systematically categorizes each runway incursion in terms of the severity of its outcome into one of four categories. Category A is the most serious and Category D is the least serious. The severity categories consider factors such as the speed and performance characteristics of the aircraft involved, the proximity of one aircraft to another aircraft or a vehicle and the type and extent of any evasive action by those involved in the event.
The Runway Incursion Assessment Team evaluates operational data pertaining to runway incursions. This team is composed of subject matter experts from air traffic, flight deck operations and airports although the composition of the team changes over time. The changing composition of the team combined with the frequently subjective nature of the available data has the potential to affect the severity ratings assigned to runway incursions. This is being addressed in the next revision of the Runway Safety Order.

Types of Runway Incursions

The FAA divides runway incursions into three error types: pilot deviations, operational errors/deviations and vehicle/pedestrian deviations. Identification of a runway incursion as a pilot deviation, an operational error/ deviation or a vehicle/pedestrian deviation is not necessarily an indication of the cause of the runway incursion; it is a classification of an error type. These error types typically refer to the last event in a chain of pilot, air traffic controller and/or vehicle operator actions that led to the runway incursion.

4.2  Performance Results FY 2004 – 2007
　
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本文鏈接地址：National Runway Safety Plan 2009-2011(5)