ETCS (European Train Control System) – A learning experience

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Network Rail was justly proud when the UK’s first operational ETCS (European Train Control System) was commissioned back in October 2010 on the short Harlech-Pwllheli section of the Cambrian Coast line. This was reported in Issue 74 (December 2010) of the rail engineer. Another milestone has since been achieved when the full Cambrian line was converted to ETCS operation on the 26th March 2011, covering the sections from Shrewsbury to Aberystwyth and Harlech. The IRSE was fortunate to obtain a technical visit to the project a week later. This gave an insight as to how the system has worked since the original commissioning and to learn of any issues raised now that the full line is operational both for the Cambrian train service and for the wider ETCS/ERTMS application to other routes.

Controlling the line

The Machynlleth signalling centre has acquired a busy atmosphere by controlling 215km of route and many more train movements. Two signaller positions are needed for the operation and their workload will increase further once an hourly train service is introduced initially on the Shrewsbury-Aberystwyth section. The signalling of trains is by issue of movement authorities which are akin to route setting in a more traditional electronic signalling centre (IECC).

The signaller uses a mouse to select entry and exit points on the route display screen. Normally the movement authority will be to the next passing loop but it can be to any intermediate point wherever Eurobalises are positioned. These equate to block sections and are shown at the lineside by a yellow and blue marker board. The train will communicate its position every five seconds (not every half second as was reported in December) back to the centre by GSM-R radio using its on-board odometer; its progress is shown on the screen much the same as if track circuits were being occupied. This distance reading is checked and reset when a Eurobalise is passed so that the measured distance travelled is very accurate. Should a balise be missed en route, this will not cause the train to be braked unless it is the expected balise at the end of the movement authority.

Included in the programming of the system is the linespeed data for all the sections and thus the train is under constant supervision for both speed and distance. Should a temporary speed restriction be needed then this can be programmed in at the control centre, avoiding the need to put down lineside speed markers or AWS magnets.

Train completeness is assured by the use of axle counters at every section, with the count in and out having to be identical. Should a disparity occur then procedures are put in place to either do a manual reset if safe conditions can be guaranteed or to run a ‘sweep train’ to prove the section should there be any doubt. The latter, aimed primarily at freight or engineering trains, can be disruptive.

Location specific

The Cambrian route has only one interface to the national network, at Sutton Bridge Junction near Shrewsbury. A train leaving Shrewsbury requires the driver to enter the train characteristics into the system via the cab DMI (Driver Machine Interface) screen and initially proceeds under ETCS Level 0 conditions, equating to conventional lineside signals. At Sutton Bridge the ETCS Level 2 system kicks in and the movement authority is displayed in the cab together with target speed. This transition can be done at 60mph but the train speed will change to kph at the entry point so as to be standard with equipment practice in mainland Europe. The train number entered will be five numerical digits but a conversion to the more conventional four-digit alpha-numeric description is done for display on the control centre screens.

Public road level crossings, as reported previously, can be CCTV, AHB or AOCL, depending on the expected volume of road traffic. The CCTV crossings are manually controlled and linked in to ETCS block sections such that movement authorities cannot be given unless the barriers are proved lowered. The AHB and AOCL crossings are not directly linked to the ETCS operation – nor are the user-worked crossings on private roads – but, should a problem occur, movement authorities can be restricted accordingly.

The flat rail crossing between the Cambrian and the Welsh Highland railways at Porthmadog is under the primary control of Machynlleth where an automated process for permitting movements is activated once a request from the Welsh Highland crossing controller is received. Telephonic communication is used should any clarification or difficulty arise. Initially, no movement authority was issued within a 15-minute window for WHR trains to safely cross but, with experience, this time is reducing as staff become more familiar with the procedure. Trains leaving Porthmadog Station eastwards can be safely through the crossing in around five minutes from issue of the movement authority. In the westwards direction, the signaller allows the train to leave Harlech up to the block section preceding the crossing before stopping any Welsh Highland movement.

Getting prepared

With a completely new operations process, getting the staff trained has been an important part of the build-up to commissioning. Two training rooms are provided at Machynlleth – one for signallers, the other for drivers. Both are equipped with simulators that mirror the control consoles at the centre and in the cabs. The driver training includes a simulated video image of the track ahead to represent real driving conditions as closely as possible. First step is for the driver to enter the train characteristics into the DMI including the five-digit running number. Thereafter, they will start a journey and drive in the normal way. If this journey begins at the simulated Shrewsbury, lineside signals will firstly be obeyed and then, at Sutton Bridge, the movement authority will appear with the supervised speed and distance. The journey will proceed to wherever a conclusion is decided. Both the driver and signaller simulators can be programmed with faults or unusual events with the consequential experience of what to do should it happen for real.

24 Class 158 DMUs are now equipped with the on-board ETCS kit, the main elements being a 19” rack containing the control equipment in part of the luggage area, the cab control panels and GSM-R radios, the underfloor balise reader aerial, the odometry equipment and speed sensors. An initial complaint of poor visibility on the DMI in bright sunlight has meant a new brighter screen unit being fitted. At night this proved too bright so a fold-down polarised shade is also required.

All the installation work has had to be done at a main depot as the alterations are significant. The cost per unit has been in the order of £300,000 – a significant percentage of the total project outlay of £95 million. Similarly, three Class 37s (alias 97s) have been fitted – numbers 97303/04/05 – whilst a fourth has been acquired but still awaits its ETCS kit. These trains are effectively the only rolling stock that can work the line; that in itself causes operational restrictions. The use of on-track machinery has to be done under specially designed ticket working. The line’s erstwhile steam specials are awaiting someone to come up with a design for a portable ETCS/GSM-R unit that could be mounted in the support coach.

Early experiences

It must be remembered that the Cambrian is an ‘early deployment scheme’ in which lessons will be learned for future usage of ETCS on busier lines. An immediate result is that the capacity of the GSM-R radio, with permanent use of a channel for every train in section, will be insufficient for other than secondary lines. Therefore the radio packet switching option (GPRS), which as yet is unapproved for ETCS usage, will be necessary. Trials are underway in Denmark and Norway and it is hoped that cross acceptance will allow this technology to be transferred to the UK with the approval process minimised.

The loops on the Cambrian are still limited to 15mph entry and exit, a restriction from RETB days. Now that the points are motorised, this speed limit can be increased which has already been tried at Talerddig where the loop does not coincide with a station. The extended loop at Welshpool is not yet operational owing to civil engineering problems but, without higher speeds, the long loop advantage will not be gained. A personal journey on the coastal section proved to be very slow with long waits at some passing points. Hopefully Arriva Trains Wales will seize the opportunity to use ETCS as a means of accelerating the train service on this section.

Two other quirks have also been encountered. Route setting of a movement authority automatically includes an overlap protection which, for the Cambrian, means going beyond the end of most loops. Thus it is not possible to allow two approaching trains into a loop at the same time – a reduction in flexibility from RETB operation. And when approaching such as a controlled level crossing, a ‘release speed’ is indicated to the driver that indicates the ongoing linespeed for the next section. This has been confused with a movement authority and a SPAD has resulted. The system protection kicked in which, in itself, was valuable proving.

It must be stressed that these are early days and changes to the operation will be made in due course to fit the Cambrian requirements. The question of changing overlap conditions will have to be set against the risk of occasional working of engineering trains, with the reduced braking characteristics that these have.

Focus on the future

Future ETCS/ERTMS projects now focus on the north end of the Hertford loop and the central section of Thameslink. These will give better indications of how the system will perform in dense traffic conditions. Thereafter, the GWML and the ECML will be the first main line applications. A dominant issue is retrofitting rolling stock and, as such, all new trains being ordered will either be fitted with ETCS equipment or with the basic wiring and space allocations to enable later fitting to be done at much reduced cost.

ERTMS remains a difficult commercial scenario. Train companies need a fair amount of convincing that they should be responsible for fitting the trains and training the drivers. So much water has yet to pass under the bridge before all aspects of ETCS operation become a norm. The Cambrian is however exposing many of these issues, which is what was intended.

2 COMMENTS

  1. Strangely it doesn’t seem to mention all the delays it’s caused Arriva Trains Wales trains which effects everybody who wants to travel on them or the fact it’s 2.5 years late and however many thousands (if not millions) over budget.

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