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Aviation Safety Targets for Effective Regulation

European Union
Complete with results
Geo-spatial type
Project Acronym
STRIA Roadmaps
Transport mode
Airborne icon
Transport policies
Transport sectors
Passenger transport,
Freight transport


Background & Policy context

ASTER is a project carried out on behalf of DGVII of the European Commission in 2000-2001. The ASTER project has been initiated in response to Key action 2.2 of the Fifth Framework Programme (‘Competitive & Sustainable Growth’) of the European Commission.


The main objective of the ASTER research is the development of a methodology that enables safety targets to be set and optimised for each of the participants in the air transport system, to achieve the optimum level of safety for the system as a whole. To support this process, means were developed for assessing the safety benefits of any changes, including changes in legislation/rulemaking, in relation to the cost of implementing those changes. Current methodologies in support of risk based regulation for the air transport system are restricted to the aircraft and its systems, do not adequately support a total aviation system approach, and do not allow effective cost-benefit assessment.


Methods that are currently being used in aerospace for setting target levels of safety were analysed. The analyses included strengths, weaknesses and developments in the current use of safety targets. A comparative analysis with the rail and nuclear power sector was performed.

All elements of the Air Transport System (ATS) were analysed and their ownership defined, including cross relationships. The relationships between ATS elements and causal factors of accidents and incidents were investigated and subsequently modelled and parameterised into a scenario based accident risk model. The accident risk model uses a taxonomy of causal factors that is based upon the International Civil Aviation Organisation (ICAO) Accident/Incident Data Report (ADREP) standard. Accidents and incidents are described as a sequence of events with descriptive and explanatory factors. The identification of relationships between causal factors is supported by a functional model of the Air Transport System. The functional model assists in identifying affected elements in the system. The accident risk model and the functional model were combined and quantified in a Bayesian Belief Network.


Parent Programmes
Institution Type
Public institution
Institution Name
European Commission, Directorate-General for Energy and Transport (DG TREN)
Type of funding
Public (EU)


The results of the work were integrated into a method that enables assessments of how the difference between the Target Level of Safety (TLS) and the current level of safety can be bridged in the most cost-effective manner. A handbook that described application of the method was developed and illustrated with a case study that compares four inherently different measures to address the wake vortex hazard:

  1. Wake vortex prediction, detection and warning on airports;
  2. Airborne wake vortex detection and warning;
  3. Wake vortex avoiding landing procedures;
  4. Active wake vortex suppression system at the wing of the aircraft;
  5. Benefits and costs of all four methods are described and compared from a European perspective.


Technical Implications

No single process for establishing Target Levels of Safety (TLS) was found to be best in all situations. Therefore, the process should be appropriate for the commercial, legal and political situations of the industry concerned and should take into account technical issues and timescales. The process should also be acceptable to at least the most important stakeholders, should be clearly defined and should result in a TLS that is both achievable and not open to significant dispute.

Policy implications

It is recommended to further develop the ASTER approach to tailor it to specific users. One of the possibilities is to further develop the ASTER method into a decision support tool for a airline Maintenance Department for assistance in making decisions on non-mandatory modifications (Service Bulletins). Further research on the use of ‘equivalent fatalities’ for Target Levels of Safety (TLS) in aviation is also recommended.


Lead Organisation
EU Contribution
Partner Organisations
EU Contribution


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