Meeting CBTC interoperability challenges: a breakdown

What to Focus on to Meet CBTC Interoperability Challenges? All-Encompassing Breakdown
What to Focus on to Meet CBTC Interoperability Challenges? All-Encompassing Breakdown PSA

Up to 10 railway systems worldwide annually move to Communications-based train control (CBTC), completely or partially. For instance, last year it witnessed the first commissioning in Australia’s history of the next-generation CBTC-based signalling system on the two most loaded lines of the Melbourne Metro. BART project impresses with its large-scale target of the full system transfer (131.5 miles) to CBTC by 2030. CBTC becomes an elegant continuation of the history of multiple railway networks, some of which originated in the 19th century.

The foreseeable destination of such a history usually comes to GoA4. Well, the future belongs to CBTC without exaggeration, but there is still no single standard for CBTC equipment communication and it is not a fact that they’ll ever appear. This issue is under hot discussion since single requirements promote supplier-independent design and maintenance of the CBTC system from the one side, but standardization slows down the evolution from the other side.

The challenge of compatibility, interchangeability, and interoperability is much wider than it seems and the solution largely affects both CapEx and OpEx. This has to be handled during the whole CBTC system lifecycle. So now, CBTC’s introduction is a joint responsibility of rail authorities and suppliers to consider all possible compatibility aspects to ensure safe and reliable transportation and bolster the potential for further network development.

Core aspects of CBTC compatibility

Mostly, CBTC is an “above level” of the signalling system. Lots of rail authorities have decided to leave conventional as a fallback signalling system, which increases the safety level. Tie-ins are crucial to connect the railroad sections under conventional and digital signalling systems for continued operation and to provide system transfer during commissioning procedures. Moreover, CBTC can comprise ATP, ATO, and ATS subsystems, which widens the connectivity surface.

Factors that define the scope for compatibility:

Overlaying the legacy signalling on the wayside

It’s not rocket science to connect the legacy relay-based system with the modern microprocessor-based system when having skillful signalling engineers to build schematic diagrams. The headache comes with legacy-new microprocessor-based systems connection through the obsolete protocols. Here, engineering resources gain even greater importance to correctly simulate and update systems. These upgrades often require additional dedicated transmission modules for interfacing with legacy, which commonly complicates the system.

CBTC delivery for dispatching

A CBTC product with dispatching functionality suggests top-robust communication with the wayside equipment and real-time data transfer. By experience, such “multi-layer” work requires sustainable development and support efforts. HAL (intermediate layer) intervention may be required to provide compatibility, optimization for the processor usage, or memory issues resolution – there is enough to deal with. Comprehensive expertise in rail system development is required here to ensure impeccable end-to-end supervision.

Interoperability for system components

Since CBTC is a concept first, it doesn’t provide for compulsory products or vendors. The market is full of incompatible patented products that are not interchangeable by default. When diving into equipment design, some rail-related peculiarities may also cause incompatibility over time.

Rail cybersecurity illustration
Rail illustration (Photo: PSA)

Compatibility for CBTC equipment components: risks of the future

As with all the rail signalling systems, the CBTC-based system is intended for decades, which will inevitably lead to some standards becoming obsolete, even within one-supplier systems. PLCs, their parts, and interfaces all turn into legacy products over time and cause compatibility issues. With the maintenance process and new components addition, legacy can start to behave unpredictably. It would seem that they can be simply replaced, but are you sure to find these legacies on the market in 20-30 years? It is hard to predict how painless the CBTC maintenance will be at such time distances, as well as to calculate the demand for these outdated systems in the railway market since their replacement is often needed suddenly.

For now, let’s take an SD card. This standard is at the top: widespread and used around the world, but who can guess its position in 20 years? This is exactly what happened with PCMCIA – a widespread standard for memory cards typically used for laptops and PLCs in the early 00s. Today, it’s out of the requirements for modern digital systems, being incompatible with them. You hardly find a ready-made replacement card in the market, which requires custom engineering to comply with complex systems, such as rail signalling. In this case, you won’t be able to avoid the involvement of various suppliers.

Naturally, the top-notch standards of today will be replaced with new and more efficient ones. The fate of legacy technologies, as well as their behaviour under modern standards, is a puzzle. The best thing to be done here is to develop forward-looking strategies for CBTC maintenance with a great share of customization activities.

Updates, simulation, and testing of CBTC

CBTC is a flexible system that is designed to adjust to the conditions, needs, and standards of a specific railroad. Any infrastructural upgrade, like adding a new junction, provides the system with new functionality that also introduces incompatibility risk. The same applies to equipment upgrades, i.e. changing the configuration of the control unit or adding a more powerful processor. Thus, multiple system updates are inevitable both before and after commissioning – during the whole lifecycle. It concerns both hardware and software components of interlocking, ATP, dispatching products, and so on, through a modular design. Every time after updates, it has to be validated that one module did not affect the functionality of the others. Any tiny deviation, such as an increase in the response time, is critical here.

This is what rail companies are likely to face in the foreseeable future. Thus, advanced simulation technologies are becoming vital to validate every interlocking scenario under new system configurations. Together with enhancements for signalling tools, it is worth developing forward-looking strategies for continuous compatibility testing to ensure the system’s correct operation.

CBTC Predictive Maintenance – Protecting Against Future Challenges

Generally, compatibility issues are revealed before or right after system upgrades, but sometimes a component fails during operation, which increases the risk of a signalling failure. This is one more reason to implement a predictive maintenance approach to railways.

Predictive maintenance is a cutting-edge approach for advanced industrial systems, which relies on the detection of the very first signs of an upcoming malfunction long before it comes. This technique allows for planning only relevant maintenance activities. First, it can be successfully applied to level crossings. Equipping the level crossing for continuous data acquisition and transmission while passing it through the analytics tool provides a precise prediction of the failure, which helps avoid queues and dangerous situations on level crossings. Second, wayside controllers can be equipped correspondingly. Despite diagnostics on board, you should deliver more sensitive data to provide precise predictions.

The complexity of the CBTC may complicate the PLC data acquisition and storage as well, which would require additional embedded memory. However, there is nothing extraordinary about building analytics models for such cases – it’s only a matter of the relevant data collection and time required for neural network training. It’s fair to assume the wider adoption of IoT and AI technologies for the rail industry in the next 20 years.

Summing up on CBTC interoperability

  • CBTC implementation and maintenance is inextricably linked with addressing compatibility issues, and customization needs. It’s fully ok, but requires robust strategies to meet these challenges.
  • With time, a majority of CBTC system components will turn to legacy, and the compatibility issues will go to the new cycle.
  • A single standard for CBTC components may partially address the interoperability challenge but hardly simplify its maintenance.
  • Interoperability and compatibility challenges are ubiquitous in rail signalling systems today. The main thing when striving for compatibility is to enlist reliable engineering support to ensure the ultimate safety and performance of the developed rail signalling solutions.

Further reading:

Author: Julia Mitchell is Business Operations Manager at Professional Software Associates

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Meeting CBTC interoperability challenges: a breakdown | RailTech.com

Meeting CBTC interoperability challenges: a breakdown

What to Focus on to Meet CBTC Interoperability Challenges? All-Encompassing Breakdown
What to Focus on to Meet CBTC Interoperability Challenges? All-Encompassing Breakdown PSA

Up to 10 railway systems worldwide annually move to Communications-based train control (CBTC), completely or partially. For instance, last year it witnessed the first commissioning in Australia’s history of the next-generation CBTC-based signalling system on the two most loaded lines of the Melbourne Metro. BART project impresses with its large-scale target of the full system transfer (131.5 miles) to CBTC by 2030. CBTC becomes an elegant continuation of the history of multiple railway networks, some of which originated in the 19th century.

The foreseeable destination of such a history usually comes to GoA4. Well, the future belongs to CBTC without exaggeration, but there is still no single standard for CBTC equipment communication and it is not a fact that they’ll ever appear. This issue is under hot discussion since single requirements promote supplier-independent design and maintenance of the CBTC system from the one side, but standardization slows down the evolution from the other side.

The challenge of compatibility, interchangeability, and interoperability is much wider than it seems and the solution largely affects both CapEx and OpEx. This has to be handled during the whole CBTC system lifecycle. So now, CBTC’s introduction is a joint responsibility of rail authorities and suppliers to consider all possible compatibility aspects to ensure safe and reliable transportation and bolster the potential for further network development.

Core aspects of CBTC compatibility

Mostly, CBTC is an “above level” of the signalling system. Lots of rail authorities have decided to leave conventional as a fallback signalling system, which increases the safety level. Tie-ins are crucial to connect the railroad sections under conventional and digital signalling systems for continued operation and to provide system transfer during commissioning procedures. Moreover, CBTC can comprise ATP, ATO, and ATS subsystems, which widens the connectivity surface.

Factors that define the scope for compatibility:

Overlaying the legacy signalling on the wayside

It’s not rocket science to connect the legacy relay-based system with the modern microprocessor-based system when having skillful signalling engineers to build schematic diagrams. The headache comes with legacy-new microprocessor-based systems connection through the obsolete protocols. Here, engineering resources gain even greater importance to correctly simulate and update systems. These upgrades often require additional dedicated transmission modules for interfacing with legacy, which commonly complicates the system.

CBTC delivery for dispatching

A CBTC product with dispatching functionality suggests top-robust communication with the wayside equipment and real-time data transfer. By experience, such “multi-layer” work requires sustainable development and support efforts. HAL (intermediate layer) intervention may be required to provide compatibility, optimization for the processor usage, or memory issues resolution – there is enough to deal with. Comprehensive expertise in rail system development is required here to ensure impeccable end-to-end supervision.

Interoperability for system components

Since CBTC is a concept first, it doesn’t provide for compulsory products or vendors. The market is full of incompatible patented products that are not interchangeable by default. When diving into equipment design, some rail-related peculiarities may also cause incompatibility over time.

Rail cybersecurity illustration
Rail illustration (Photo: PSA)

Compatibility for CBTC equipment components: risks of the future

As with all the rail signalling systems, the CBTC-based system is intended for decades, which will inevitably lead to some standards becoming obsolete, even within one-supplier systems. PLCs, their parts, and interfaces all turn into legacy products over time and cause compatibility issues. With the maintenance process and new components addition, legacy can start to behave unpredictably. It would seem that they can be simply replaced, but are you sure to find these legacies on the market in 20-30 years? It is hard to predict how painless the CBTC maintenance will be at such time distances, as well as to calculate the demand for these outdated systems in the railway market since their replacement is often needed suddenly.

For now, let’s take an SD card. This standard is at the top: widespread and used around the world, but who can guess its position in 20 years? This is exactly what happened with PCMCIA – a widespread standard for memory cards typically used for laptops and PLCs in the early 00s. Today, it’s out of the requirements for modern digital systems, being incompatible with them. You hardly find a ready-made replacement card in the market, which requires custom engineering to comply with complex systems, such as rail signalling. In this case, you won’t be able to avoid the involvement of various suppliers.

Naturally, the top-notch standards of today will be replaced with new and more efficient ones. The fate of legacy technologies, as well as their behaviour under modern standards, is a puzzle. The best thing to be done here is to develop forward-looking strategies for CBTC maintenance with a great share of customization activities.

Updates, simulation, and testing of CBTC

CBTC is a flexible system that is designed to adjust to the conditions, needs, and standards of a specific railroad. Any infrastructural upgrade, like adding a new junction, provides the system with new functionality that also introduces incompatibility risk. The same applies to equipment upgrades, i.e. changing the configuration of the control unit or adding a more powerful processor. Thus, multiple system updates are inevitable both before and after commissioning – during the whole lifecycle. It concerns both hardware and software components of interlocking, ATP, dispatching products, and so on, through a modular design. Every time after updates, it has to be validated that one module did not affect the functionality of the others. Any tiny deviation, such as an increase in the response time, is critical here.

This is what rail companies are likely to face in the foreseeable future. Thus, advanced simulation technologies are becoming vital to validate every interlocking scenario under new system configurations. Together with enhancements for signalling tools, it is worth developing forward-looking strategies for continuous compatibility testing to ensure the system’s correct operation.

CBTC Predictive Maintenance – Protecting Against Future Challenges

Generally, compatibility issues are revealed before or right after system upgrades, but sometimes a component fails during operation, which increases the risk of a signalling failure. This is one more reason to implement a predictive maintenance approach to railways.

Predictive maintenance is a cutting-edge approach for advanced industrial systems, which relies on the detection of the very first signs of an upcoming malfunction long before it comes. This technique allows for planning only relevant maintenance activities. First, it can be successfully applied to level crossings. Equipping the level crossing for continuous data acquisition and transmission while passing it through the analytics tool provides a precise prediction of the failure, which helps avoid queues and dangerous situations on level crossings. Second, wayside controllers can be equipped correspondingly. Despite diagnostics on board, you should deliver more sensitive data to provide precise predictions.

The complexity of the CBTC may complicate the PLC data acquisition and storage as well, which would require additional embedded memory. However, there is nothing extraordinary about building analytics models for such cases – it’s only a matter of the relevant data collection and time required for neural network training. It’s fair to assume the wider adoption of IoT and AI technologies for the rail industry in the next 20 years.

Summing up on CBTC interoperability

  • CBTC implementation and maintenance is inextricably linked with addressing compatibility issues, and customization needs. It’s fully ok, but requires robust strategies to meet these challenges.
  • With time, a majority of CBTC system components will turn to legacy, and the compatibility issues will go to the new cycle.
  • A single standard for CBTC components may partially address the interoperability challenge but hardly simplify its maintenance.
  • Interoperability and compatibility challenges are ubiquitous in rail signalling systems today. The main thing when striving for compatibility is to enlist reliable engineering support to ensure the ultimate safety and performance of the developed rail signalling solutions.

Further reading:

Author: Julia Mitchell is Business Operations Manager at Professional Software Associates

Add your comment

characters remaining.

Log in through one of the following social media partners to comment.