LONDON’s Thameslink network will make history at the end of this year with the first-ever commercial deployment of Automatic Train Operation (ATO) over ETCS on a main line railway. Thameslink forms a cross-city link across London by grouping lines to the north and south of the city and connecting them through an 8km central core section. Infrastructure manager Network Rail (NR) worked closely with the supply chain to research how ATO over ETCS Level 2 could help to deliver metro headways in the core.
From December, capacity on the core section will be increased from 16 trains per direction per hour to 24, with the ability to accommodate a recovery frequency of up to 30 trains per hour.
NR had an advantage in that infrastructure and rolling stock were being upgraded in parallel as part of the €7bn Thameslink Programme, and one supplier (Siemens) was chosen to deliver both. The train supplier was therefore given the opportunity to define the trackside specification it needed for the ATO. Laboratory testing of the system began in January 2013, a year before rolling stock production started and nearly four years before the scheduled start ofpassenger operation with ATO.
The International Association of Public Transport (UITP) Grades of Automation (GoA) system defines the degree of automation according to the level of responsibility assigned to the train control system. There are five grades:
- GoA 0: manual operation with no automatic train protection
- GoA 1: manual operation with automatic train protection
- GoA 2: semi-automatic train operation (STO)
- GoA 3: driverless train operation (DTO), and
- GoA 4: unattended train operation (UTO).
ATO applications, including Thameslink, are GoA 2. Under GoA 2 the driver is responsible for closing the passenger doors and operating the train in the event of disruption, but setting the train in motion and stopping are performed automatically.
Metros have been operating GoA 2 for more than 40 years and indeed more than 70 metro lines in 40 cities around the globe are now running at GoA 4. Applying ATO in a mainline environment where different train types running on different routes share the same infrastructure is inevitably a more complex proposition, but as Thameslink demonstrates, it is now becoming technically feasible.
The application of ATO over ETCS was first considered by a TEN-T project in 2011, and this study concluded that ATO solutions could deliver higher capacity and lower energy consumption on the main line. The ERTMS Users Group subsequently devised an operational concept for main line GoA 2-4 and this in turn fed into the development of a Unisig technical specification for GoA 2.
The specification was handed to the EU Agency for Railways for inclusion in ERTMS Baseline 3 Revision 2, but ultimately further discussions were required around the application of ATO over ETCS, which meant it was not feasible to include it in this release. This means there is no provision for ATO over ETCS in the Control Command and Signalling TSI (TSI CCS).
Another key development in the evolution of main line ATO was the four-year Next Generation Train Control (NGTC) project, which examined the commonalities and differences in functionalities between ETCS and CBTC with the aim of driving the technical convergence of the two systems with a combined main line-urban rail specification for ATO and ATP. NGTC was completed last year and found that converging ATP is not feasible and only a “common core” of ATO can be shared between main line and urban rail applications.
“The big benefit of this project was that the people involved talked to each other, there was an exchange of knowledge between main line engineers, to get some knowledge about how ATO works in the urban rail world,” Dr Roman Treydel told delegates at the Railtech Intelligent Rail Summit in Vienna on November 28 2017. “This has fed into the next project, part of Shift2Rail, so we understand all the difficulties when developing ATO specifications.”
The Shift2Rail joint technology initiative is driving research into ATO for mainline applications through its Innovation Programme 2, which seeks to develop and validate a standard ATO system up to GoA 3/4 over ETCS.
Shift2Rail’s work on ATO has been split into two workstreams because of the different level of maturity of the GoAs. The GoA 1 and 2 workstream is due to conclude its work in 2019 and builds a technical specification for main line ATO around the existing operational concept. Suppliers have begun development work for the project, with Alstom and Siemens expected to complete test benches by the end of this year, with trials expected to take place on a pilot line in Britain in 2019. The EU Agency for Railways is expected to issue a technical opinion on GoA 2 next year, enabling the specification to be fixed, and the aim is to include ATO in the next TSI CCS, which is due to be issued in 2022.
The specification of GoA 3 and 4 will be developed using a model-based systems engineering approach. The workstream will run until 2023 or 2024, and in the later stages it will bring in GoA 1 and 2 to ensure there is a single, consistent specification spanning all GoAs. “This is important for mainline transitions, because you can’t assume on the main line that all trains will be GoA 4,” Treydel says. “In the meantime, GoA 2 is already fully specified, it’s already really mature, and the concept is very stable. It gives you a capacity increase, more punctuality and less energy consumption.”
According to Dr Xiaolu Rao, senior system engineer for Systransit, Switzerland, one challenge for main line ATO will be optimising both the onboard and infrastructure to achieve the benefits desired by the operator. “You have an inner control loop onboard - the driver controlling the train - and an outer control loop, which is the link between the train and the infrastructure via the dispatcher,” she explains. “The Traffic Management System (TMS) enhances the outer loop for network-wide optimisation, but optimising the outer loop has no direct influence on the train control. People are also starting to optimise onboard through a Driver Advisory System (DAS) or ATO, where all of the effort takes place onboard. Here we can improve the train driving, but this offers no direct network-wide optimisation in terms of conflict resolution.
“ATO on the main line means facing the reality that there are a lot of conflicts. We can’t ignore that, so only doing ATO onboard is not enough. TMS and ATO need to be integrated and share knowledge for optimisation. This isn’t easy to do. What are the detailed functions of the TMS and ATO? What data needs to be communicated between the two? We need a specification for this. Integrating the TMS with the onboard means we will be more able to reduce the risk of conflicts.”
Another challenge is that different operators in different markets have different priorities when it comes to ATO. These could include increasing capacity, reducing energy consumption, enhancing ride comfort, or improving timekeeping. Some of these goals will contradict each other - it is difficult to optimise the capacity of a section of track while minimising energy consumption. Furthermore, priorities may vary according to the time of day and levels of demand.
On the Dutch network, where 10-minute interval inter-city services were introduced for the first time in December, the focus is on squeezing more capacity out of already well-used infrastructure. “ATO is a need-to-have for the future of rail,” explains Mr Alfons Schaafsma, innovation and development advisor for Dutch infrastructure manager Prorail. “Business cases should be the main driver for ATO so it’s important to go for the level of automation you need to achieve your business case objectives. Eindhoven - Amsterdam might have a business case for GoA 2 because there’s an inter-city train every 10 minutes, a regional train every 15 minutes, and a freight train every 30 minutes, which needs to run precisely in its path.”
However, as with any form of automation, the human factor is a critical consideration. “Man is the measure of automation,” Schaafsma says. “Successful implementation requires a prominent role for the human factor early in the process - perhaps earlier than we are used to. The needs of operators should determine the pace of automation. It’s also important to involve people in technical tests so they can experience their future.”
Schaafsma also questions the extent to which drivers should be responsible for safety when operating under GoA 2. “On the Betuweroute [freight corridor], you have 100km between noise screens and hardly any other trains, so how can the driver be alert enough to take control if necessary? How is safety guaranteed when a driver takes over? How can the driver monitor whether the automated unit is performing correctly? We also need to consider how we avoid the underload and overload of drivers and signallers, and how we can make automation attractive to drivers to smooth the acceptance of change.”
While Thameslink sets a precedent for ATO over ETCS, ATO has also been successfully applied over other signalling systems. Paris RER Line A is one of the busiest suburban rail lines in the world, carrying 1.2 million passengers a day, or up to 70,000 passengers per direction per hour. The line consists of a central core with two branches to the east of the city and three in the west, and RER trains share tracks with other train types at the periphery of the system.
Alstom has developed an ATO solution for the line under a €20m contract awarded by Paris Transport Authority (RATP). The system was commissioned in 2017, controlling pairs of five-car MI09 double-deck EMUs and older MI2N trains on the central core. The line’s entire fleet of 100 trains will be equipped by the end of this year.
Alstom says it has adopted a project-specific virtual testing platform for the project, with a simulator to accelerate the system maturity growth. Simulation covered the entire line and RATP provided Sacem hardware and software for the virtual test benches.
In China, ATO has been rolled out on the Dongguan - Huizhou and Zhaoqing - Foshan inter-city lines using a solution developed by Alstom and its Casco joint venture. The ATO is an overlay on CTCS Level 2 (equivalent to ETCS Level 1) and has been in operation since March 2016 using a 200km/h CRH6 train.
As standards develop, ATO looks set to become a widespread feature of main line networks in the 2020s, laying the ground for a longer-term move towards driverless operation.