Currently located around five dozen rail transit lines around the world, Thales’ SelTrac ™ CBTC (Communications-Based Train Control) urban signaling technology is now in its eight generation.
Thales SelTrac ™ G8 is the latest iteration of technology that has evolved from an inductive circuit platform based on a side / center office to a platform with radio frequency (radio frequency) concentrated on board (vehicle), offering a level of flexibility and configuration options.
“CBTC has been a global rail signaling solution for decades,” said Rob Vanderwecht, senior manager of SelTrac’s product line. “Over time, our system has evolved into different technologies or building blocks. In principle, what we see is much more a need for evolution. There is a faster pace of technological change and the needs that drive this change are accelerating. “
Among these needs is what Thales calls “aging management.” There are two forms: “technical obsolescence” and “functional obsolescence”.
A component, product, or service is described as technically obsolete when it is replaced by something that may not be backward compatible. With CBTC, these are primarily computer hardware and software and communications. For example, the aging of a microprocessor has the potential to make the LLRU (the lowest level removable device), usually a board, obsolete. Unless a board with the same FFF (shape, fit and function) can be extracted, the whole subsystem is at risk of aging.
Functional aging occurs when the CBTC system cannot be adapted to meet changing needs. For example, for CBTC systems that are currently “automated” (GoA2 and GoA3), operators may want the option to upgrade to a fully automated, unsupervised driverless operation (GoA4). They may want to upgrade train-to-path communications from an inductive loop to RF: 802.11 or LTE (Long-Term Evolution). Enabling this requires a complete system architecture capable of supporting progressive upgrades.
This is exactly what SelTrac ™ G8 is designed to do. “It’s based on what we call our new digital architecture,” says Vanderwecht. “Thales bases it on common hardware platforms with the ability to abstract different layers of software. Simply put, this means that we can deploy proven hardware in a number of different configurations and upgrade it with software later. As a prime example, you can install the hardware today, configure it as a stand-alone lock, and upgrade it to the CBTC Zone Controller in the future using the same hardware. Scalability or flexibility is a key feature. Evolution will be important as technology changes. With systems like CBTC with a lifespan of 20 or 30 years, operators will want the ability to add the latest technologies that provide new features and functionalities. You don’t want to age an entire system because one element of it is outdated. This is key for our customers in terms of reducing life cycle costs. This is the main theme for the next generation G8. In other words, these are a number of different applications on the same hardware platform and architecture, in which the application software is changed for new implementations. “
“The key thing we’re looking for in the SelTrac-G8 is abandoned systems,” says Vanderwecht. “Everyone’s focus is on reducing costs, and something we’ve always focused on is reducing the amount of equipment on the track or along the road. “We have already done this by eliminating the need for a secondary form of vehicle detection. In this new architecture, we have implemented a new roadside objective controller for devices such as arrows, emergency stop buttons and doors on the platform screen. The package is small, very configurable and available. We can create the right amount of hardware to be located in different side situations. There is a lot of flexibility. “
Another important feature of the SelTrac-G8 is its “radio-diagnostic” approach. “Radio technology has been growing over the last few years and we have already passed this point of a universal radio solution for the CBTC system,” says Vanderwecht. “In the past, we have adopted various radio technologies and what we are doing here is to modulate the radio communication aspect of our solution – something we call a modular communication gateway. This gives us a great deal of flexibility in supporting LTE, public or private, and a number of unlicensed spectrum radios. We can evolve to 5G if we want, and we can even combine radio technologies to expand the geographic system, such as LTE in the surrounding area and unlicensed high-speed radios at the heart of the network. We can now choose the radio technology that best suits the application, again, to reduce costs and reduce implementation time. “
For example, a line may have a combination of terrain that creates variability in radio propagation – the overhead tangential track, where line of sight communications are not an issue. Tunnels. Curves passing through deep cuts. The radio diagnostic function of SelTrac ™ G8 allows it to be equipped with what works best in a certain environment. “In a tunnel environment where you will not be broadcast on a public LTE radio network, you will install your own infrastructure,” Vanderwecht said. “You can now choose an unlicensed 2.4 GHz band or 5.9 GHz, a licensed frequency band set by the European Commission for urban railways. It remains to be seen how popular this type of blended technology will be, but there is definitely room for improvement, especially for operators who may have existing radio technology and want to expand with another type. We see much greater interest in private LTE networks. “
The sheer volume of data communications needed for everything from train control to customer information systems means that cybersecurity is a growing concern for operators. “Aspects of cybersecurity must be designed in a system from the beginning,” Vanderwecht said. “Obviously, when adopting different wireless technologies, you still have to consider the implications for cybersecurity, say, public LTE cloud or private deployment. This is one of the features of the SelTrac ™ G8 communication gateway. For roadside architecture, as we begin to deploy more object controllers or remote I / O, we need to consider aspects of cybersecurity of communications. As we begin to move away from special optical lines between locations, adopting new technologies such as a software-defined network and different methods of connecting everything, we must rely on “zero security” approaches. This will always be a big focus because you need it with an improved, improving digital architecture like this. “
Beyond train control
While the CBTC’s core function is critical to train safety control, there are many other features that can be included – everything from passenger information systems to on-board real-time health monitoring and diagnostics. For the transit system, everything is based on providing a reliable service – trains appear when they need to and attract customers to their destinations safely and on time. As such, data management has become critical.
“Much of the SelTrac-G8 architecture is the core protocols and software and data services that tie it all together,” explains Vanderwecht. “They have been improved not only for cybersecurity, but also for many diagnostic and data management services that will allow us to monitor and troubleshoot and perform predictive maintenance. They allow so many other important basic functions. CBTC data is of course our top priority. We make sure that there is quality service and latency so that there are no safety consequences. Then we have different levels of service or different types of data streams that will support data diagnostics, troubleshooting or passenger information. When designed correctly, you have a lot of flexibility and features. “
Next generation positioning system
Another key aspect of the SelTrac ™ G8 is its compatibility with Thales’ NGPS (Next Generation Positioning System), an autonomous train positioning system that has gone through proof of concept with the MTA New York City Transit. Instead of conventional mileage and markers, NGPS uses inertial navigation, radar and radio or GPS. These functions are combined with a 3D reference map to determine the exact position of the train. In the future, LIDAR (Light Detection and Range) and high-resolution camcorders will provide additional data to enable features such as obstacle detection.
“Economical and easy to deploy, autonomous positioning is more reliable than conventional systems,” says Vanderwecht. “This level of technology will provide many benefits and functionality for our CBTC system. This will allow us to deploy faster, reduce costs and improve productivity. By doing it right and setting it up, the SelTrac ™ G8 is ready to get NGPS. It is ready for autonomy and we designed the product so that we can take advantage of these benefits. “
For CBTC abandoned field systems, installation, testing and life cycle costs are critical considerations. “Because you’re migrating to CBTC, you don’t have much access to the track, and that will affect your deployment schedule,” Vanderwecht said. “NGPS is based on sensors that are no longer mounted under the vehicle, so it facilitates application and installation. However, we are trying to get to the point where the benefits of an on-board autonomy or positioning system are recognized much earlier. You don’t have to wait for a detailed deployment to be installed before you can see the benefits. If you move more technology on board as the trains are located, you immediately start to see some of the benefits. The NYCT is a driving force for the NGPS platform and for the adoption of UWB, which we demonstrated in early 2020. “
Considerations after a pandemic
“We are now going through interesting times with COVID-19 and we probably don’t fully realize the impact it has on urban transport systems,” says Vanderwecht. “One of the most important advantages of the SelTrac ™ G8 architecture and its flexibility is that it can adapt much faster to a rapidly changing environment. If new communication technologies or something else emerges, it helps us as a company to be much more flexible. Some operators believe that the transition to CBTC is a big step, but the evolutionary nature of our architecture means that it is less of an approach than the Big Bang. We believe that the aspect of our system shows the benefits of taking the first steps. This is a good thing. “