ETCS Level 2 replaces flawed vision
Roger Ford reports on the progress with Railtrack's latest plans for resignalling the West Coast Main Line, following the collapse of the company's original transmission-based signalling strategy
DECEMBER 9 1999 was highlighted on Railtrack's West Coast Route Modernisation project chart with a black diamond. That day was to see the completion of a major review of the project and progress so far. When 'Black Diamond Day' came, the review confirmed that the ambitious plans for resignalling the entire route with a moving-block transmission-based Train Control System had collapsed.
As a result of the review, Railtrack admitted that the overall WCRM infrastructure project cost would jump from £2·2bn to £5·8bn (RG 1.00 p16). While signalling was not the only problem contributing to the increase, the enforced change in signalling strategy represented £1·4bn of the cost over-run.
Moving-block TCS had emerged as the preferred solution from a 1995 consultants' study into modernisation of the West Coast Main Line. Transmitting signal information from a central interlocking to a driver's display in each cab by radio would eliminate much of the conventional lineside signalling equipment and its associated maintenance.
According to the study, these savings were big enough to justify investment of £1·3bn in bringing the WCML infrastructure up to modern standards. Moving-block, an inherent feature of the system, would ease the growing capacity constraints. The consultants also believed that the combination of existing digital radio and vital safety software techniques in other safety-critical industries could be taken 'off the shelf' and applied to the WCML.
Railtrack accepted the proposals. But when TCS was put out to tender, only the European railway signalling majors were serious contenders. In April 1996 GEC Alsthom Signalling (now Alstom) and Transig (a consortium of Adtranz and Westinghouse) were awarded development contracts. But 18 months later new bids were invited for a single company or consortium to act as prime contractor for the WCML resignalling. Only two offers were received: Alstom with Alcatel, against Adtranz Signal and Westinghouse Signals.
Questioned on the technical risk of TCS at the time, Railtrack's then Director of Engineering & Production, Prof Brian Mellitt, was bullish. 'All the components of this system - mobile phones, fail safe computers - have been around for a long time', he declared. 'The real challenge is systems integration, getting them to work together and be reliable. The technical issues are much less challenging than the organisational and management issues.'
Alstom was selected as preferred bidder in May 1998 and began a nine-month project definition phase which would also refine cost estimates, then quoted in the somewhat broad range £500m to £1bn. In June 1999, Alstom began the design phase under a second £35m contract. But Railtrack had already begun a major review of the whole WCRM, which was clearly running into cost and time problems.
Virgin Trains had been expressing growing concern over Railtrack's ability to deliver the cab signalling essential for the operation of its Pendolino fleet at 225 km/h on the WCML from May 2005. This requirement was part of a £600m contract between Virgin and Railtrack incorporating penalties of up to £250m.
When the review team reported on Black Diamond Day, Railtrack estimated only a 5% chance that Alstom Signalling would have moving block operational by 2005. TCS was abandoned. 'We don't want a Jubilee line on the WCML', commented Railtrack Commercial Director Richard Middleton, referring to London Underground's similar problems with the introduction of moving-block signalling.
A complex compromise was the only way forward to meet the rapidly-shortening implementation timetable. Radio-based moving-block cab signalling would have been, in effect, Level 3 of the European Train Control System. The logical fall-back position after Black Diamond Day was to implement the simpler ETCS Level 2. This retains conventional lineside interlockings, but transmits the signalling aspects to the train by radio for display in the cab. Much of the extra signalling cost reflects the need to replace 72 interlockings along the route which would have been eliminated by TCS.
Under the original scheme, conventional signalling would in any case have been retained at busy locations, where TCS could not match the precision of track-circuited interlockings with colourlight signals. 'Islands' of conventional signalling were always planned for the station approaches at Manchester South, Birmingham New Street and Euston, together with part of the Trent Valley route.
These contracts were unaffected by the change of policy and all are due to be commissioned under Phase 1 of the WCRM in time to allow 200 km/h running to start in June 2002.
Westinghouse Signals has completed the Euston area resignalling using Mk II Solid State Interlockings. Axle counters have been used for train detection to eliminate track circuit unreliability in the station throat.
At Manchester South, Ansaldo's ACC computer-based interlocking was selected under Railtrack's policy of introducing new signalling technology to the British market. Completion of this scheme has now been brought forward to autumn 2001. However, this depends on obtaining safety case acceptance for the Ansaldo CBI and its trackside equipment to a short timescale. Railtrack confirmed last month that it was still stuck in the approvals process.
WS Atkins is responsible for the other two 'islands'. These are the Proof House Junction scheme on the eastern approach to Birmingham New Street station, and the Stoke - Colwich corridor in North Staffordshire. Both are SSI based, with the North Staffs line also using axle counters for train detection.
Raising line speeds to 200 km/h from June 2002 will require changes to 400 signals between Euston and Crewe. At about 100 locations signals are being relocated to increase sighting times or, if this is not possible, repeaters are being installed. For the rest, sighting improvements are required, for example, by cutting back lineside vegetation.
Resignalling for ETCS
With lineside interlockings to be retained throughout, Railtrack's WCML resignalling strategy has effectively been divided at Crewe. To the north, new signalling was installed as part of the 1974 electrification and is not due for replacement until 2010-12. Southwards, the signalling was installed for the earlier electrification in 1960-67 and will become life-expired over the next five years.
Reflecting this situation, Railtrack plans to install Eurobalise-based ETCS Level 1 north of Crewe, as a simple way of providing Automatic Train Protection with the existing signalling. A maximum line speed of 200 km/h will apply to the Virgin Pendolino trains on this section.
South of Crewe, the contractual introduction of 225 km/h running from May 2005 is dependent on the provision of cab signalling, which is required by British safety regulations. Over the next four years, Railtrack will be replacing interlockings at a time when second-generation Computer Based Interlockings are still at an early stage of the safety acceptance process. In addition to the Ansaldo ACC installation at Manchester, both Adtranz Signal and Siemens are developing pilot CBI applications for the British network.
Meanwhile, Alstom Signalling and Westinghouse Signals are offering the proven first-generation SSI equipment, and both companies are developing a migration strategy to give this product the computer-based design facilities provided by the latest CBI.
Railtrack therefore has to decide between the off-the-shelf availability of enhanced SSI and the longer term potential of CBI, which, it claims, offers operational advantages at busy locations such as Watford and Rugby, but is still subject to acceptance. A complicating factor is the condition and residual life of the existing equipment. At Rugby, for example, ageing track circuits are already causing problems. The track layout here is also likely to be remodelled for higher speeds. These factors favour an early application of CBI.
The signalling companies are currently submitting prices for resignalling south of Crewe. Alliance contracts are likely to be negotiated in which Railtrack and its contractors share performance risks and rewards.
Under the original moving-block proposals, the WCML was to have been controlled from a single Network Management Centre, which would also have housed the central interlocking and the Radio Block Centre. Railtrack went out to tender for the NMC in parallel with the moving-block signalling, and the contract was awarded to Union Switch & Signal in October 1998.
Following a development phase US&S was asked in January this year to accelerate the project. Railtrack is particularly keen to have the operational control facilities of the NMC available by the time that 200 km/h running starts in June 2002. But the NMC building at Saltley, near Birmingham, only went out to tender inSeptember, with completion scheduled for the end of 2001.
Over the past 10 to 15 years, large British resignalling schemes have been based around SSI and the Integrated Electronic Control Centre developed by British Rail Research. IECC control features include computer-based Automatic Route Setting.
Tendering for the resignalling schemes south of Crewe is based on the premise that they will have minimal local control facilities. Railtrack's intention was that as various projects were commissioned, they would be interfaced with the NMC, so that route setting could be determined by the US&S 'decision tools'. The resulting routing strategies would then be telephoned to the local signallers. This interim arrangement would operate until resignalling was completed and the NMC took over direct control and regulation of all trains in 2005.
However, Railtrack is now having second thoughts about this strategy, as real-time route setting at one step removed would be impractical on such a busy route. Bids were invited last month for five 'Interim Control Centres' which must be operational by June 2002. Likely to be installed at Crewe, Stoke, Rugby, Nuneaton and Wembley, these will provide enhanced local control capability until the NMC is completed, and may be retained as an emergency standby in the longer term.
Radio communications hub
Also to be housed in the NMC building at Saltley will be the Radio Block Centre, effectively an intelligent telecommunications switching facility. Signal aspects will be transmitted by radio or landline from the lineside interlockings to the RBC in real time. Information on speed restrictions, gradients and other data needed for ATP will be stored in the RBC. This data will be combined with the signal settings and transmitted to each train by digital radio.
Complicating the design of the RBC is the decision to resignal the route with a mix of SSI and CBI. Under the original scheme, the RBC would have interfaced directly with the central interlocking which would have been SSI-based. Now Railtrack has specified that the RBC will have to be able to interface with two proprietary designs of CBI in addition to SSI. The main complication arises because SSI uses a decentralised architecture while CBI has a centralised structure. According to Alstom Signalling, meeting this requirement will not be simple, 'but it can be done'.
WCML signalling: who is doing what
ETCS contractor Alstom Signalling
Radio Block Centre Alstom Signalling
Sub contractors: GSM-R digital radio Siemens
Base station land lines Marconi
Network Management Centre Ansaldo (US&S)
Euston area Westinghouse Signals
Proof House Junction WS Atkins
North Staffs Corridor WS Atkins
Manchester South Ansaldo (CSEE)