Blockchain for safety-critical interlocking logic

Innovation Public Safety

Blockchain makes it possible to run several computers in a network and thus increase reliability. Especially in safety-critical areas such as interlockings, this enables the use of standard computers where special hardware would otherwise have to be used. In the TARO project, SCS has developed a concept and prototype for the use of blockchain for interlocking logic.

  • Initial situation

    Safety-critical components are expensive because they require specialized hardware and development must meet strict guidelines.

  • Solution SCS

    Safety-critical logic is placed on a private blockchain as a smart contract. The private blockchain serves as a secure system that meets the high reliability requirements.

  • Added value

    Costs can be saved by combining "standard" blockchain technology and "standard" computers. Once such a system is certified, only the smart contract needs to be certified.

Project insights

When designing a blockchain solution, it is important to ensure that the blockchain is only used for those aspects that are absolutely necessary. In our case, for the aspects that are safety-critical. What is not or less safety critical can be implemented with technologies that have higher throughput, larger storage and lower development costs.

In our case, it has been shown that a simple reservation system is the minimal solution that meets all requirements. For each train, the track sections, switches, level crossings, ... to be used are reserved in good time in advance. The reservation includes in particular the position of the component (e.g. the switch). This reservation is the digital form of a green signal. The train checks whether it has the reservation for the next track section and therefore knows whether it is allowed to travel on it. If the blockchain says "no" or he loses the connection to the system, this corresponds to the red signal. The train must stop.

Other information is not managed on the blockchain. For example, the topology information (how the track sections and switches are connected) is not on the blockchain. The "operational state" is also important. If one wants to know the current state of a component, a blockchain is reliable but not fast. Therefore, we have added the "Operational State" as an additional layer, which corresponds to a veto right. In concrete terms, this means that the train will only pass over the switch if the blockchain and the switch itself say "yes". If one of them says "no", this corresponds to a red signal.

In addition to the concept, SCS has built a prototype blockchain and a simulator, which together demonstrate that the system works:

The concept and demonstrator were discussed with experts from ÖBB Infrastruktur AG and other project partners and were deemed to be a sensible solution by all sides. Furthermore, performance measurements were made, which show that the performance is sufficient for the regional rail sector.

Before blockchain is actually used productively for safety-critical logic, there are certainly still some hurdles to overcome. One of the most important questions is how blockchain can be certified for safety-critical applications. In terms of its basic principle, blockchain brings exactly the features we need for a reliable, tamper-proof system. At the same time, it is a new technology with much still in flux. Nevertheless, we see a big potential for the use of private blockchains for reliable systems.

About the Taro project

The TARO project ("Towards Automated Railway Operation") is a multi-year research and development project led by the ÖBB Group. Together with 17 partners, numerous aspects are being worked on with regard to the digitalization and partial automation of the overall rail system. One of the project's focal points deals with "regional rail technology of the future". The Federal Ministry for Climate Protection, Environment, Energy, Mobility, Innovation and Technology (BMK) is funding the project with a total of EUR 3.5 million from the RTI-Program Mobility of the Future, which is handled by the Austrian Research Promotion Agency (FFG). More information can also be found at

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