PLC technology in a rail environment

16 March 2023
Image of a rail traffic control light on green.
Amey Consulting is introducing new cost-effective solutions for signalling safety based on the latest programmable logic controller technology

Amey Consulting continually seeks to increase efficiency, reduce costs and cut carbon in the development and operation of UK infrastructure through innovation in design and technology. An excellent example of this is the application of the latest programmable logic controller (PLC) safety technology to railway signalling.

German company Hima supplies PLCs to many safety-related industries including nuclear and chemical plants, oil and gas, and amusement parks. Its HIMatrix PLC has an established safety record and meets the high safety integrity level (SIL 4) required for applications such as rail signalling, where a failure can lead to serious loss of life. The PLC is already in use on rail networks throughout Europe, as both an interlocking and level crossing controller.

Amey recognised that the Hima PLC offers several benefits over the proprietary safety systems traditionally used for signalling in the UK. It is cheaper, more flexible, compact in size and easily programmable. Amey decided to partner with Sella Controls (Hima’s UK arm) to develop the PLC into an alternative signalling control solution for the UK market.

Before such a system could be introduced, Network Rail safety approval was required. Amey and Sella Controls worked with NR to build a safety case, including the development of a fully tested working prototype. The final stage of the process was an operational trial, conducted at Magdalen Road level crossing in NR’s Anglia region.

The PLC has performed well. Its modular design allows for a flexible approach to specific level crossing locations. It is easily programmable using standard languages, requiring no rail-specific training. It has a powerful diagnostic capability, providing direct fault-finding information with the potential to incorporate condition monitoring and alarms.

Based on the success of the safety case and the trial, the PLC has been included in Amey Consulting’s innovative design for the Taff’s Well Depot on the Core Valley Lines in Wales. It plays a central role in the depot’s interlocking and signalling control system, due for commissioning in early 2023.

Amey believes the Hima PLC technology provides a superior, cost-effective alternative to the proprietary safety systems currently in use in the UK. Unlike those products, the Hima technology is open access with a control system based on commercial off the shelf (COTS) components, introducing competition into a previously closed market. Any supplier or contractor can license the technology to bid for signalling work across Network Rail.

By using the latest safety industry components instead of traditional British Rail-style relays and components, installations are protected against obsolescence. The wide take-up of the technology across Europe further reduces the risk, as future developments in safety control would need to be backwards compatible. Amey is already working on new applications for the PLC in UK rail environments.

In addition, the PLC offers significant sustainability benefits. It is not only smaller and cheaper to manufacture and install, its relatively low power consumption means it can work with an offgrid renewable power supply, such as solar panels and wind turbines. It is being tested with wireless and radio networks in Europe in order to avoid the need for costly cabling.

The Hima PLC project is an excellent example of how Amey’s willingness to adopt new technology and learn from other sectors can cut costs and add real value to a UK rail industry struggling to shake off outdated practices and embrace an open, digital future.