Case study: Replacing a relay interlocking with an open PLC solution

Learnings from the Stockholm Metro’s open signaling pilot

Traditionally, computer-based signaling systems come with long support and maintenance commitments, often lasting 25–40 years. The downside is the risk of vendor lock-in. Changes, upgrades, and even component replacements can become dependent on a single supplier’s roadmap.

In this webinar, we’ll share learnings from an ongoing pilot project in which the Stockholm Metro is replacing a legacy relay-based signaling system with a modern PLC-based SIL 4 solution. The pilot explores what it really takes to design and maintain an open signaling system over time so that maintenance and upgrades can be sourced from an open market, with 100% guaranteed safety.

You’ll get a practical view of the technical choices, project setup, and verification & validation approach, what’s working, what’s been harder than expected, and what we’d recommend if you’re considering a similar modernization.