Reliable, certified software for railway safety systems – Blog Solwit

Reliable, certified software for railway safety systems


SIL4 software conforming to ISO50128, ISO50159

IEEE 20119 multilevel testing and documentation

TÜV SÜD certification

SIL4 software conforming to ISO50128, ISO50159

IEEE 20119 multilevel testing and documentation

Important information




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Voestalpine is a global capital group that manufactures, integrates, installs, and maintains devices and systems that improve the efficiency and safety of rail and road transport.


The client needed a partner to develop and test safety-critical software and to support certification in accordance with the standards for rail transport.

The client was looking for a full service partner who would provide safety-critical software in rail traffic. The task of the system was to control the occupancy of railway sections by detecting passing vehicles. In addition, the client needed a solution compliant with CENELEC SIL-3 and SIL-4 standards. It was also crucial not only to create software on hardware belonging to another partner, but also to certify and complete test and hardware documentation. And that’s what we did.


The client wanted to enter new market segment and didn’t have a sufficiently mature and efficient testing process. They wanted to focus on the business domain and searched for a partner that could deliver them complex testing service, and then provide support in the certification process.


The customer has broad railway domain know-how and hardware development capabilities, but was unable to grow and sustain a software development team with strong quality orientation and mature development practices. They were searching for a reliable partner that could help them develop and deliver a high-quality product line based on next-generation hardware.


Within our comprehensive services, we completed two extensive projects with the client. The first was to provide extensive programming services. Design, development, and integration with Signaling Card hardware, as well as delivery of applications, integration tests and validation. The second project involved building and carrying out the test process, preparation of documentation, and support in the certification process.

1. Software that meets high-security standards
Project goals:
– monitoring and control of the – occupancy of sections of railway tracks
– safety control of trains moving over the sensor on railway tracks
– integration with Signaling Card hardware
– safety-critical software

What have we delivered?
– firmware that meets the requirements of the SIL4 integrity level and ISO50128 and ISO50159 standards
– .NET software enabling configuration of the entire system
– development of code critical for communication and security
– development of embedded software – design, expansion, and integration with signaling equipment
– application development, multi-level testing, and integration validation
– support in the system approval process

2. Software tests that meet the highest SIL-4 railway safety requirements

What have we delivered?
– multi-level tests
– framework for system tests
– developing software architecture, design, test strategies, test plans, test conditions, and test cases
– test automation structures (test bundles, stubs, and test cases)
– fully developed and documented test processes
– definition and implementation of test coverage and static analysis tools
– schemes for test and development documents
– implementation of DOORS in the area of testing
– Organized test execution and reporting mechanism
– laboratory (average power density 500W/m2)
– technical documentation of test processes and test results


The product has been certified by TÜV SÜD, and the testing process has been positively verified and approved by the certification body.

We helped the client through the certification process and introduction of the product to the market.

Because our team eased the work of Voestalpine employees, they were able to concentrate their efforts on other tasks. In addition, the client used a scalable resource-on-demand solution, which resulted in cost optimization in the software development process. Importantly, 6 months after the start of cooperation on the embedded system software, we were invited to extend the project into validation of solutions and application development (additional 3 HC).

Upon completion of the project, Voestalpine has high-quality software compliant with CENELEC SIL-3 and SIL-4 standards, which meets the high functionality and safety requirements for railway track occupancy control systems.


Finally, we supported Voestalpine in the certification process. We represented the client in the testing process before the TÜV SÜD certification body and we have been supporting the Voestalpine team continuously since 2015.


“Solwit S.A. was responsible for the implementation of part of the embedded software for the system, in accordance with the rigors of the industry railway standards, and for ensuring the quality of the software in an automated test environment. Today, the UniAC (2) system is implemented by railway line operators all over the world, ensuring rail traffic safety in line with standards. Currently Solwit, as a permanent partner of Voestalpine SIGNALING, participates in the processes of further maintenance and development of the system, at the same time providing support in adapting the solution to the requirements of individual target markets.”
Przemysław Wołoszyk, Development Director, Voestalpine SIGNALING Sopot Sp. z o.o.


Railway industry standards: CENELEC SIL4 and ISO 50126, ISO 50128, ISO 50129, ISO 50159, redundancy, MISRA C 2012, UML modeling, PIC32 uC CAN family, SPI, Ethernet, EtherCAT


SVN, Redmine, Enterprise Architect, MPLAB X IDE, Pc-Lint, Cppcheck, Code collaborator, Gerrit, Vera ++, Uncrustify, Jira, Redmine, Jenkins


C, C#, .NET, ASM, PIC32, ARM

CI environment

Jenkins, Unity, dedicated validation model, network equipment and embedded devices, plus elements of railway infrastructure

Test documentation in accordance with IEEE 20119

Settlement model

Time & Material