The laboratory software (AQL) Qualification of the RATP

RATP has successfully invested and developed ways of independently verifying the safety of the critical software deployed on its rail network by means of a very powerful instrumental method called PERF (Proof Executed over a Retro engineered Formal model). This method has now demonstrated its efficiency and represents the state of the art as regards software validation.

In the framework of PEEE (ERTMS level 2 on LGV EE) project and in response to the request of Réseau Ferré de France (RFF), RATP has applied this approach with success onto the ADA source code of the RBC (Radio Block Centre) software (wayside equipment of ERTMS levels 2 and 3).

The “usual” safety analysis has been performed by the supplier’s teams, based on a combination of manual ADA code reviews and test campaigns, in order to demonstrate the safety level as requested by RFF and SNCF.

In a parallel and disconnected activity, the PERF approach led by RATP made also possible to validate the expected safety level, and in addition to reveal axes of improvement with regards to requirement specification and coding.

RFF and SNCF can now rely on innovative tools allowing them to rationalize efforts to be made to obtain the safety demonstration of software embedded onto safety critical wayside and onboard equipments in order to address future developments and deployments of ERTMS.