Historical Background

After working in the field of real time systems development, the founders of CLEARSY discovered formal methods and their interest in the 1990s.
The founders developed and industrialised what was to be the first real industrial software development tool using the formal B method.

Atelier B, génie logiciel

Atelier B

This tool, Atelier B, has since enabled the production of numerous fully mathematically proven safety software products that meet the strictest standards.

These industrial successes in the software field have also revealed the importance of the quality of the system specifications in which critical software is implemented. CLEARSY, in collaboration with the inventor of the method and laboratories, has developed formal system modelling techniques.

Several industrial projects have already been able to use these techniques to specify systems (components, electronic architecture and PLC systems).

All these experiences have convinced CLEARSY’s engineers that formal methods are tools that allow systems to be mastered, and that the certification of systems and software is greatly facilitated.

CLEARSY positioning

  • To position itself in the market for the realisation of security systems
  • To use the formal B method to build the systems and software it is entrusted with.


An important decision

CLEARSY innovates on the market of systems and software development by introducing the use of formal methods.The use of modelling tools and techniques allows us to capitalise and constantly improve the quality of the systems we produce.The realisation of operational systems encourages us to implement and develop formal tools that are increasingly accessible to engineers.

CLEARSY thus wishes to be a driving force in the techniques and formal tools for the development of certified safety systems.

Key dates

From 1990 to 2000

1993 : Start of industrialisation of Atelier B for use in METEOR safety software
1994 : Distribution of the first version of Atelier B
1998 : First Atelier B industrial version and commissioning of the METEOR metro

From 2000 to 2010

2001 : Creation of CLEARSY to develop the B method. Two agencies: Aix-en-Provence and Paris.
2002 : First version of a system-level formal language. Use of the B method for the modelling of the operating principles of the Peugeot 206, 307, 407 cars.
2003 : Creation of the Functional Safety activity

2004 : Provision of a free tool for academics to use the B method: B4Free
2005 : Specification of industrial systems with the B method.
2006 : Beta test version of a formal system specification tool: Composys. – Commissioning of the Coppilot safety system for the control of landing doors on line 13.
2007 : Development of Brama, a B model graphical animation tool. Installation of the COPP system on the Châtillon station in Paris, integrating safety equipment developed by CLEARSY.
2008 : Provision of a free version of Atelier B 4.0 and release of some modules as open-source.
From 2010 to 2021

2010 : Prime contractor for the deployment of the COPP system developed by CLEARSY, on twelve stations of line 13 of the Paris Metro. Assistance in the evaluation of the safety systems of the Flushing and Culver lines for the New York City underground.
2011 : Development of 3 systems in the framework of the Regiolis project led by Alstom: SAS and GAPS/UP2S. Commissioning of KFS SIL2 on the Rhônexpress tramway in Lyon.

2012: Commissioning of the system for detecting individuals in dangerous gaps on line 1 in Paris. Opening of a facility in Lyon.
2013: Distribution of a SIL4 level safety relay according to industrial standard 61508, developed by CLEARSY. Distribution agreement for systems developed by the RATP. Signing of a contract for the installation of the control system for the landing doors on the new Sao Paulo Monorail.
2014: Commissioning of the automatic stop system for Valenciennes trams (KFS SIL2).
2016: CLEARSY, an EDF/Septen design office, for a period of 5 years, in the field of safety classified control-command of PWR&EPR plants.
2016: Launch of the SIL4 relay game: RS4.
2017: inauguration of the platform screen door control system  for the Stockholm metro.
2018: acquisition on July 12, 2018 of ERSA (European Rail Software Applications), a specialist in ERTMS/ETCS simulation tools and test benches.
2019: Already at CEA and EDF, CLEARSY enters ITER.
2019: The safety critical data validation tool of CLEARSY is rated T2.
2020: New logo, new signature: Safety Solutions Designer.
2020: The first secure supervision system for fire safety systems in the Paris metro made by CLEARSY is put into service.
2021: CLEARSY’s vital computer is certified at SIL4 level.