There have been several articles already on ERTMS (European Rail Traffic Management System) published in The Rail Engineer, and there will be many more as the years progress. This vitally important system for the future of signalling and train control is slowly rolling out across Europe. Writes Clive Kessell
Here in the UK, another milestone has been reached with testing of several equipment types on the Hertford Loop test track in north London. Known as ENIF (ERTMS National Integration Facility), it is an important preliminary before future main line deployment.
The need for a test site
One of the specified features of ERTMS is that it must be interoperable. This means that the manufacturers of both lineside infrastructure equipment and train-borne radios and control units must work seamlessly with each other. It sounds simple. However, in the European development process, it has been anything but.
Designers of signalling systems have a long pedigree of making things different, both to be different from other suppliers and as new technology has emerged. Signalling also has to facilitate operating rules, these being different in most countries. When signalling was primarily infrastructure based, it did not matter too much but, once signalling kit becomes partially train borne, it is essential that the various piece parts are compatible with each other.
It could be argued that, providing the specification is rigorous enough, then interoperability will happen by default. Sadly, this has not been the case and much development aggravation has occurred in mainland Europe. Network Rail, being mindful of these problems, has set out to prove that different types of equipment will work harmoniously together. Hence the ENIF project.
What the tests will achieve
ERTMS has two main constituent parts – ETCS (European Train Control System) and GSM-R (the rail adaptation of the public GSM mobile radio standard). The first represents the signalling element and the second the transmission path between control centre and train.
The Network Rail framework contract to supply of ETCS has selected four companies to compete for the long term business – Signalling Solutions Ltd (a consortium of Alstom and Balfour Beatty), Infrasig (a collaboration between Bombardier and Carillion), Siemens Rail Automation (formerly Invensys / Westinghouse) and Ansaldo STS (which supplied the pilot ERTMS project on the Cambrian route) and these companies have to prove the compatibility of their equipment with each other.
The line between Hertford North and Stevenage is double track but, in off peak hours, it has only one train per hour in each direction. Hence a five-mile section of the down line has been made available as a test track with single line working on the up line for the passenger service. A changeover switch in Kings Cross power box enables the test track section to be isolated on demand and, once switched in, testing can take place within the five-mile limit without any control from KX.
A Class 313 EMU has been converted to be the test train and is fitted with Alstom ETCS train equipment. The four suppliers have all provided ground equipment, mainly the track-mounted balises that give position information and the interface to the control system. Each company is allotted specific days when their system is under test, these being conducted from the ENIF control centre which is located in Hitchin.
ETCS still requires computer-based interlockings (or even relay interlockings with the right interface equipment) for the safe setting of routes and junction control. Between these and the control centre screens is a Radio Block Centre (RBC) that interprets the requirements for the ongoing route and translates this into a Movement Authority (MA) that is sent to the train. The interlocking and RBC are proprietary to the particular supplier and, at the Hitchin site, each of these is given a test lab where their control centre is installed. These labs are security controlled so that no-one can steal ideas from another party.
The route setting screens are similar to those that might be seen in any modern IECC using a mouse or tracker ball to select the route of the intended train path.
A summary of the four systems is as follows:
- SSL (Alstom) – interlocking is the latest Smartlock 400 with the RBC based on similar technology. MAs are shown slightly differently to conventional route setting. ETCS will offer less restrictive approach control to junctions and similarly easier permissive entry to occupied platforms.
- Ansaldo STS – uses an SEI interlocking linked to its own RBC. The equipment is essentially similar to that at Machynlleth on the Cambrian line.
- Infrasig (Bombardier) – interlocking is the latest EbiLock product with a compatible RBC.
- Siemens (ex Invensys) – interlocking is the Westlock product and compatible RBC. Has conventional route setting procedures and the system will also be used for testing ETCS with an ATO overlay for Thameslink.
During the allocated test period, each product controls the test track section and issues MAs to the test train for the test programme of the day. Conditions to be tested include the introduction of temporary speed restrictions and emergency stops.
Since the line retains conventional signals for normal operation, the test train has to pass these. It is possible to set an MA that allows the train past a red signal but this is considered disconcerting for drivers and thus the ENIF control is configured to ensure such signals always show a proceed aspect. The balise operation is slightly different for each manufacturer’s kit and thus these have to be reconfigured prior to the particular day’s testing. The connection of the individual firm’s control to the ground equipment uses the FTN network and is configured by jack-in plugs and sockets on a patch panel.
Each firm is also required to model ETCS for the London to Heathrow and London to Wood Green routes so as to simulate capacity on a busy piece of railway. A temptation to be resisted will be requests from operators to customise the system for ‘special’ UK requirements. The ultimate goal is for any train arriving through the Channel Tunnel to be capable of working seamlessly to the British ERTMS package.
The train-borne system
- The EVC (European Vital Computer) that receives and interprets the commands from the RBC;
- The driver’s control panel showing the Movement Authority as a moving band on the outside of the speedometer and with the driver having to keep the speed inside this limit otherwise alarms and braking will occur;
- A Eurobalise reader mounted under the train to give position information and data for forthcoming stations, level crossings, etc;
- Two forms of odometry, both doppler radar and a traditional tachometer, to measure distance from each balise;
- A GSM-R data radio to receive the radio-borne MA instructions.
Although only one type of train kit is installed on the test train, other types of rolling stock will come to Hertford for compatibility testing. It is estimated that the design, fabrication and fitting of a first-in-class installation takes 18 months with the train being out of service for around 12-16 weeks. Thereafter, fleet fitment should be about two weeks for each vehicle. Driver training is expected to take 2 weeks for full ETCS conditions.
A lesson learned from the Cambrian is that retro-fitting is both messy and costly. There will be franchise implications in the future and ETCS fitment may well become part of a franchise condition. Whenever possible, ETCS will be part of a fleet renewal programme and all vehicles ordered after Jan 2012 or delivered after Jan 2015 must have provision for the system.
Network Rail is likely to sponsor the ROSCOs (Rolling Stock Companies) for retro fitting on a national fleet basis. Similarly for the 850 ‘go anywhere’ freight locos, funding will be made available for the retrofit programme. Network Rail’s fleet of engineering trains and on-track machines must also be fitted but more difficult are locomotives associated with charter and heritage operations.
A solution for steam engines is proving elusive but where there is a will, there will be a way.
GSM-R as a track-to-train voice facility is now well established on Network Rail. However, the radio network has also to be a bearer for ETCS and currently this uses circuit switching in that, once a train is logged on, it remains connected for the duration of the journey. This is not an efficient use of spectrum and channel limitations will not permit ETCS to be used in busy traffic areas.
The solution is packet switching (known as GPRS) and entails sending packets of data to a train when required. Signal engineers have reservations about the integrity of this but recognise the advantages. As a result, GPRS is being tested at ENIF on behalf of the ERTMS User Group based in Brussels. So far the results are encouraging and the UK is leading the way for Europe and wider climes.
When GSM-R is used to support ETCS, it is usual to provide additional lineside base stations to provide continuous coverage should a single base station fail. This has happened at Hertford with part of the testing including operation with a switched-out base station.
The Thameslink dimension
The decision by the Thamelink upgrade authorities to use ERTMS for its central London core brings about new challenges. To achieve the 24 trains per hour criteria, automatic train operation is needed and this means providing an ATO overlay to the basic ETCS package.
Again, the UK will be pioneering this facility for Europe. Siemens has the contract to provide the system but sensibly has requested using the Hertford track to test it. Part of the line will thus replicate the Farringdon to Blackfriars section, needing additional signals and links to the Thameslink development centre in James Forbes House near London Bridge.
With the main ETCS integration tests largely complete, the test line will be handed over to Siemens and the Thameslink team in November 2014.
Having witnessed the problems with the roll out of ERTMS in Europe, Network Rail is wise to provide the Hertford / Hitchin test facility. If nothing else, it has driven the message home to manufacturers that interoperability must be achieved.
Although the software level of the infrastructure equipment is version 2.3.0d which will eventually need upgrading to 3.0.0 or later derivatives, this should happen as a cross industry roll out with insistence on backward compatibility.
Hertford has its limitations; the maximum line speed is only 70kph and there are no junctions under ETCS control. A next step is to equip the Old Dalby test line where speeds up to 180kph are possible. It will also give unlimited access, not possible at Hertford as the line has to be handed back for peak hours.
The main line deployment of ERTMS is aligned to route modernisation so time is short to get the major contracts let. Currently, future implementation plans are:
- Great Western main line Paddington to Heathrow – 2017
- Great Western main line Paddington to Bristol – 2019
- Thameslink fleet service – 2018
- East Coast main line Kings Cross to Wood Green 2018
- Northern City line Moorgate to Drayton Park- 2018
- East Coast main line Kings Cross to Doncaster – 2020
- Midland main line – 2022
One of the suppliers is intent on offering ERTMS Level 3 as part of the package using experience gained in Kazakhstan. This is intended as a potential package for secondary routes and has the advantage of further reducing lineside infrastructure.
ERTMS will reduce the cost of signalling but, above all, it will yield important capacity benefits. It sits alongside the 12 regional operating centres and the traffic management systems as the cornerstone of Network Rail’s train control strategy. Much is at stake but with customer and industry working together, it will succeed.
Thanks are expressed to the ERTMS programme, project and engineering teams for facilitating the visit and the openness in explaining the system.