The Aviation Safety Monitor measures safety margins by estimating the frequency, duration, and severity of buffer encroachments. A buffer encroachment occurs when an aircraft pair is predicted to be closer than the minimum separation standard – both lateral and vertical – for that airspace. The encroachment algorithms account for aircraft type (heavy and other aircraft), airspace rules, horizontal distance between successive aircraft, and vertical separation. The FAA has defined minimum separation standards when aircraft are under Instrument Flight Rules (IFR). The buffer encroachment algorithms use these separation standards as a baseline to define adequate safety margin levels.
