Risk analysis tool

Our methodology used to classify safety-related occurrences in the air traffic management (ATM).

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The Risk Analysis Tool (RAT) is a methodology used to classify safety-related occurrences (incidents or serious incidents) in the air traffic management (ATM) domain. The methodology analyses two types of occurrences: operational and technical occurrences.

RAT is a sub-tool of the TOKAI risk analysis tool.


TOKAI is the toolkit for air traffic management occurrence investigation.


RAT allows an occurrence to be rated based on facts collected during the safety investigation process, answering to a predefined set of questions, thus permitting users to assess the degree of risk and put in place corrective actions with the appropriate level of priority.

For ATM technical occurrences, the severity and overall probability of recurrence is determined based on a combination of criteria, such as service provided and failure modes of systems that support air traffic service (ATS) provision.

The various combinations have been mapped in a look-up table that is at the heart of the methodology to define the safety risk posed by the combination of the technical failures and types of ATS provided.

In order to ensure harmonised determination of the severity of ATM technical occurrences and the risk posed to the ATM system, RAT has been designed and developed independently of any particular ATM system design.

RAT is not a risk mitigation tool. It facilitates the analysis of a single event in order to acquire an understanding of the factors involved, and then place the event in context with other events. The occurrence assessment indicates the risk that occurrence posed to the ATM system, in particular to the ground (the ATC centre) but also to the overall ATM system (ground and airborne, including crews).

This methodology has been adopted by the EU Single European Sky Performance Scheme and it is incorporated into EU law.

    Usage options

    As RAT is a sub-tool of the TOKAI tool, the same principles apply. There are two technical solutions:

    • a solution hosted at EUROCONTROL; 
      Small to medium-sized ANSPs usually opt for this, allowing them to save on administration costs and to use the tool as an online service.
    • a full local installation of the software;
      This is the preferred option for larger ANSPs who can make available the infrastructure and labour to maintain the TOKAI tool at their own site.


    The tool is available to any ANSP upon signing a licence and service level (SLA) and a Non-disclosure agreement (NDA).

    The tool is available to users from the ECAC Member States for free. All other users are subject to an annual licence fee.

    For further information about the access conditions, please contact us via the contact form on this page.