Software Engineer – Railway Systems & PLC

Building better and safer isn’t a slogan, but the way we show up in the world.

It’s how we make sure technology speaks not only in code, but with meaning: better technologies, better ways of working, and more inclusive communities. We align with what matters for people and for the planet, actively nurturing it to be better and safer. At the center, it’s our people who power everything we do. It’s their talent, drive and different ways of thinking that keep us moving forward, pushing the limits of what’s possible.

The Role

We are looking for a driven engineer to join our growing railway systems team. You’ll be at the heart of delivering mission-critical software for train control systems — working to the highest safety standards (SIL2) and directly shaping how millions of passengers travel safely every day.

What you will do

• Design, develop, and validate PLC-based software for safety-critical railway applications, following EN 50657 standards up to SIL2.
• Apply your railway domain knowledge across the full lifecycle of the train control systems — from requirements through to integration.
• Collaborate with cross-functional teams (Systems, V&V, Safety) to ensure software quality and traceability throughout development.
• Produce and review technical documentation including Software Design Specifications, Software Architecture Specifications, and safety cases to SIL2 requirements.

Who You Are

• Minimum 2 years of experience in the railway domain, specifically in Train Control and Management Systems.
• Hands-on PLC programming experience.
• Proven track record delivering software up to SIL2 (EN 50657 or equivalent).
• You take ownership — you don't wait to be told there's a problem; you raise it and help solve it.
• Continuously improve your craft — staying current with railway standards, tooling, and best practices, and sharing knowledge across the team.
• Strong written and verbal communication in English; French is a nice to have.

What We Offer

Critical Software is a company built on technical excellence, trust, and genuine care for the work we do. As a Software Engineer, you will:

• Work on technology that matters — your code will be part of systems where safety is non-negotiable, directly impacting the reliability of rail networks in operation.
• Join a team with depth — collaborate with experienced engineers across Systems, V&V, and Safety.
• Grow your career — with access to continuous learning, internal mobility, and the support of a team that invests in your development.
• Work flexibly — across our offices in Lisbon, Porto, Coimbra, or Viseu, with a hybrid working model.
• Recharge when you need it — Sabbatical programme.

We also offer a competitive compensation package, health insurance, and the chance to do meaningful work alongside engineers who genuinely care about what they build.

Every day we embrace new missions across industries as diverse as aerospace, space, defense, transport, telecoms, government, energy, finance and healthcare. Now, the real question is: are you ready to join us and help make the world a better and safer place?

Critical Software is proud to be a Benefit Corporation. A Benefit Corporation differs from a standard corporation (C-Corporation): It is a for-profit business entity, legally defined in the US and other jurisdictions, whose legally defined goals include the positive impact on society, workers, the community and the environment, in addition to profit.

We are an equal opportunity workplace and committed to allow candidates with disabilities or neurodevelopmental conditions to prove their competencies to their full potential. We are willing to move the barriers that may prevent you from demonstrating that you are the right candidate for this role, so please let us know if you need some adjustment in your recruitment process.

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