Skip to main content
Article thumbnail
Location of Repository

Are There Good Air Traffic Management Safety Indicators For Very Safe Systems?

By Peter Brooker


European Air Traffic Management is extremely safe. The drawback to this safety record is that it is very difficult to estimate what the ‘underlying’ accident rate for mid-air collisions is now, or to detect any changes over time. The aim is to see if it possible to construct simple ATM safety indicators that correlate with this underlying accident rate. A perfect indicator would be simple to comprehend and capable of being calculated by a checklist process. This problem has been examined by a combination of analogies with simple ‘defensive’ systems with Markov process properties. An important concept is that of ‘system control’: the ability to determine the outcome against reasonably foreseen changes and variations of system parameters The statistical distribution of future incidents has been analysed by focusing on an index – the CPI – of separation at the Closest Point of Approach. A promising indicator is ‘Incident Not Resolved by ATC’, INRA, incidents in which the ground ATC defences have been ‘used up’. ATM Incidents can also be categorised in other ways: two examples are reviewed: the risk-bearing category for Airproxes and ‘risk of collision/severity’ scores. The second is more promising conceptually, but the existing scoring system has not been demonstrated to have the properties necessary to derive risk estimates. The key question is: if someone says they know how to make a good estimate of the underlying accident rate, then how could this claim be tested? If it correlates very well with INRA, then what would be the argument for saying that it is a better indicator

Publisher: Cambridge University Press
Year: 2007
OAI identifier:
Provided by: Cranfield CERES

Suggested articles


  1. (2002). A Study of Incident Reporting in Air Traffic Control - Moral Dilemmas and the Prospects of a Reporting Culture Based on Professional Ethics.
  2. (2006). Air Traffic Management Accident Risk Part 1: The Limits of Realistic Modelling. Safety Science In press. doi
  3. (2002). Automatic Safety Monitoring’ in Air Traffic Control -Achievements and Perspectives. Workshop on the Investigation and Reporting of Incidents and Accidents
  4. (2004). Consistent and Up-To-Date Aviation Safety Targets. Aeronautical Journal.
  5. (2004). Defining and Analyzing Precursors. Accident Precursor Analysis and Management: Reducing Technological Risk through
  6. (2005). European ACAS Operational Monitoring
  7. (2006). Home Page.
  8. (2002). PRC [Eurocontrol Performance Review Commission]
  9. (2005). Reducing Mid-Air Collision Risk in Controlled Airspace: Lessons from Hazardous Incidents. Safety Science. doi
  10. (1997). Selling the Invisible: A Field Guide to Modern Marketing. doi
  11. (2004). The Rules, and History of the Rules, of Association Football.

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.