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Design of SIL4 actuators for Rail Track Circuits for HS (High Speed) railway lines.

SERVICE MERCATO CLIENT Azienda multinazionale operante nel mercato ferroviario YEAR 2019 - 2021 in progress


The STDS LF (Smart Train Detection System Low Frequency) is a fully digital low frequency SIL4 track circuit system (50Hz/83.3Hz and 178Hz), which exploits the benefits of increased immunity and the flexibility of digital systems.

The STDS AF (Smart Train Detection System Audio Frequency) is the new generation Alstom solution for the management of audio frequency track circuits (AF TC – Audio Frequency Track Circuit) without the use of insulated mechanical coupling.

The main function of both systems is the detection of train presence by generating and receiving a specific modulated vital signal to and from the track, in order to determine the status of the track circuit (free/busy).


Both systems, characterised by different architectures and operating principles, required

  • analysis of product input requirements;
  • analysis of product Sw and/or HW requirements and tracking down to low-level components;
  • drafting/updating of product design documents (the activity also included dealing with results from Safety, V&V checks and changes during the development cycle);
  • drafting/updating of product manuals;
  • SysML model definition: SysML/UML model design, the model had to include Operational, Functional, and Constructional levels;
  • support to the design team for the EoP (End of Phase) reviews and for the GR (Gate Reviews) according to the ALSTOM DFQ V cycle;
  • knowledge of the 50126, 50128 and 50129 reference standards.

Project challenge

To support the client in the management, verification and validation of requirements throughout the entire product development cycle, thus allowing savings on re-work and non-quality costs. To identify any critical issues in the document management, requirements management, Change Request management, and configuration management processes by proposing solutions to optimise workflow and avoid non-compliances.


Having analysed and understood the client’s development process flows, NIER developed a systematic working method based on the management of parallel products and developments that enables the client’s gate reviews to be managed effectively.

Execution phases


Analysis of the documentation based on the task to be performed;


Analysis of the standard (where applicable);


Process analysis (where applicable);


Drawing up of plans: Project Plan (PMP), Configuration Management Plan (CMP), Engineering Management Plan (EMP), Requirements Management Plan (RMP);


Requirements specification and propagation along the system/product life cycle;


Support to the design team for acting on comments from V&V, Quality, and Safety;


Requirements coverage matrices and requirements management tool configuration (e.g. Reqtify);


Consolidation of the document;


Management of activities for Gate Reviews;


Document baseline creation at the end of each Gate Review.

Achieved results

NIER’s precise and timely work contributed to keeping the design team’s deliverables on schedule. In particular, the support provided during the functional specification phase and in the subsequent phases contributed to the improvement of the quality of the system documentation by reducing re-work costs, thanks to the early detection of anomalies during development and updating.

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