Chiltern Renaissance – The Evergreen Success

Written by Clive Kessell for the rail engineer

August 2011 saw the implementation of the latest series of improvements to the Chiltern Railway’s Marylebone to Birmingham line.

Bannered under the name Evergreen 3, this stage is almost the final programme of work to restore the route to its past glories.

The line has seen mixed fortunes over time. One of the last railways to be built, it opened in 1906 as the GW&GC Joint line, itself linking up a series of other lines to form a rival to the LNWR route northwards from London.

The line was constructed with the lessons of avoiding flat junctions in mind, with Northolt, Ashenden and Aynho all having flyovers to minimise conflicting moves.

Principal stations had main lines through the middle with loops to accommodate the platforms, Denham, Gerrards Cross, Beaconsfield, Princes Risborough and Bicester North being examples.

The route settled down to providing a Paddington – Birmingham service as an alternative to the WCML via Rugby, as well as enabling the GCR to have a second route into its Marylebone terminus. Birmingham was around 2 hours from the capital by the best trains, regardless of route.

The GW route came into prominence in the 1960s during the electrification of the West Coast Main Line with virtually all Birmingham traffic being put to the Paddington line.

Rationalisation and Decline

In the aftermath of Beeching and the then thinking that two lines between principal cities were not needed, the Great Western route suffered a downgrading. The Great Central northwards was closed, negating the need for Ashenden Junction.

Station through lines were removed and the entire route from Princes Risborough to Aynho (where it joined the GW Oxford – Banbury line) was singled having only a passing loop at Bicester.

The remaining train service was concentrated on Marylebone with only one train per day running to Paddington

Little more than an outer suburban service, trains were formed of ageing DMUs and reliability suffered accordingly.

Even Marylebone was considered for closure at one time, but the remaining traffic was sufficient to make it impractical to accommodate at other termini. So the line survived, and with privatisation came the realisation that considerable untapped potential was there for the taking.

Chiltern Railways and Evergreen 1

Led by career railwaymen and women, Chiltern Railways quickly gained an understanding of what needed to be done to give a better service.

The initial priority was to eliminate the long single-line section. In partnership with Railtrack, this was done as the Evergreen 1 project in two stages: firstly from Princes Risborough to Bicester, and then from Bicester to Ayhno.

Many lessons were learned from this project as re-doubling a line is not simply a matter of laying a second track. Over time infrastructure elements such as cable routes, signals and power supply points all encroach on the track bed while the remaining track is sometimes slewed to a central position.

Thus the entire section had to be rebuilt including the provision of two new platforms at Haddenham & Thame Parkway station (opened in 1990) as the original platform had been constructed on the old track-bed. Signalling the two lines for bi-directional running was a sensible future proofing move.

The concentration of traffic onto a single platform at Princes Risborough was another encumbrance and the down platform was restored at the same time, albeit without the through centre lines. While the cost was considerable, restoring a two track railway gave immediate benefits in timetable reliability.

Evergreen 2

The increasing train service required additional capacity at Marylebone, so, under the Evergreen 2 project, that terminus was given another 2 platforms making 6 in total, something it had never had in its entire history.

With new Networker Turbo trains coming on stream, the opportunities for expanding services beyond Banbury became obvious and in association with Centro, who were busy restoring Birmingham Snow Hill and providing through platforms at Birmingham Moor St, sufficient capacity was available for Chiltern Railway to run to Birmingham.

Evergreen 2 also included the provision of a new train servicing depot at Wembley together with speed improvements at Beaconsfield and various signalling modifications. However, this was not the end of the story as overall journey times needed to be reduced still further to compete with both the WCML and the M40.

Evergreen 3

A critical appraisal of options revealed that work at seven locations was necessary to get the much needed line speed improvements. All have now been implemented.

  • Aynho Junction. The 50mph turnouts for the Marylebone line have been raised to 90mph in the up direction and 85mph for the down line coming off the flyover with new high speed points connecting to the Oxford lines. In addition, a new facing crossover makes the junction fully reversible so that bi-directional working can be implemented when necessary over the Aynho to Princes Risborough line. Having a 7 day railway is very much in the minds of the Chiltern Railways management, as well as benefiting other operators using the Didcot to Chester line. The Ayhno works were completed in March 2011
  • Bicester. The removal of the old through lines meant that the remaining running lines were slewed over to the platforms, necessitating a speed restriction. In the up (London) direction, the platform has now been built out so that the line can assume its former straight alignment. This work was also completed in March 2011 and resulted in an increase in linespeed from 25mph to 100 mph.
  • Princes Risborough. As at Bicester, the slewing of the up line to the platform alignment imposed a speed restriction. In addition, conflicts were caused by the branch line services to Aylesbury also using that platform. Since the fast Birmingham services will not stop at this station, the solution has been to restore the up through line with connections at both ends for the platform line. Both up lines have been made reversible. This work was done between 22 – 28 August.
  • High Wycombe. A new positioning of the north end crossover enables higher speeds to be achieved through the station for non stopping services.
  • Gerrards Cross. The construction works for the artificial Tesco tunnel to facilitate a store car park needed a siding to be provided for the works trains and the former turnback siding was converted temporarily as a freight facility. The unfortunate collapse of the tunnel during the work was an unwanted hindrance but led to one wag coining the phrase ‘You shop, We drop’. With the incident now well in the past, the opportunity has been seized to future-proof the siding and extend it to create an 8-car turnback facility for inner suburban services. Another turnback has been provided from the platform on the down line.
  • Northolt Junction. The grade-separated junction favoured the ex-GW line to Paddington for higher speed. However, with virtually all services now concentrated on Marylebone and the GW route reduced to a single line, this situation needed to be remedied. The solution has been to construct a new double track formation direct from Northolt to South Ruislip, retaining the fly-under route for suburban trains needing to stop at Ruislip, with the GW line routed via a single lead connection and facing crossover. The civil works to construct the double track alignment have been complex and were described in the March and August 2011 editions of the rail engineer. The work was completed during a blockade lasting from 22 – 28 August.
  • Neasden Junction. Where the Amersham and Banbury lines diverge, the double junction restricted the latter lines to 40mph. The junction has now been remodelled as a series of single leads to permit a 75mph turnout towards Banbury. This work was carried out between 12 and 21 August during a total blockade.
  • Chiltern2
    Work in progress at Neasden. Photo: the rail engineer.

Mention must also be made of Birmingham Moor Street, where, after many months of waiting, signalling works were completed in November 2010 to bring into use the bay platforms. Chiltern Trains use these for some services as capacity at the three platform Snow Hill station (the 4th platform being used for Midland Metro tram services) is limited.

The two stations contrast greatly with Moor St being a classic design in true GW style while Snow Hill is a stark concrete edifice that compares badly to the architectural gem that was the original station.

Finance and Contracts

The Evergreen 3 project is unusual since it is an infrastructure improvement, but with financing coming entirely from Chiltern Railways. They are the Sponsor, Client and Agent. Network Rail has been a co-sponsor but also has the role of mortgagor and approver.

Costing around £250m, the justification centred on the additional passenger numbers and income that the scheme will generate. Whilst the prime work has been to provide additional trackwork, the project has involved a number of engineering disciplines.

Chiltern appointed BAM Nuttall as lead contractor to have a design and build responsibility as well as letting and managing all the principal sub contracts. These were:

  • Civil Works – BAM Ritchies constructed the Northolt double track formation.
  • Trackwork – Although Colas initially stood in after Jarvis ceased to trade, BAM Nuttall undertook much of the trackwork on their own account. Balfour Beatty carried out the work at Aynho. On-track machines and plant were provided by Colas, Balfour Beatty and Babcock Rail
  • Signalling – Atkins was responsible for the design, installation and testing of all external signalling alterations. These included the re-signalling of the junction areas as described plus the provision of many new signals mainly between High Wycombe and London to give greater spacing for the higher line speeds. All new signals are of the LED type. Preliminary Route Indicators (PRIs) were also installed to give advance warning of the direction to be taken at the higher speed junctions by means of lit right or left arrows prior to the flashing yellow aspect.
  • Marylebone IECC – Delta Rail, who as BR Research and AEA Technology were the developers of Integrated Electronic Control Centres, had the expertise to make the necessary changes to the Marylebone Signalling Centre from which the majority of the route is controlled. This involved the provision of a third complete SSI interlocking as there was insufficient capacity within the existing ones to accommodate the changes. Some re-mapping of signalling boundaries between the interlockings took place at the same time. Changes to the train describer function and the associated cab secure radio link also had to be undertaken.
  • Telecoms – Telent undertook all the work associated with cable alterations and new or re-located SPTs.
  • ATP – Alcatel supplied the original SELCAB equipment to the Chilterns route, one of two BR trial Automatic Protection Systems in the early 1990s (the other was on the GW main line) as a forerunner of TPWS and ERTMS. The system extended only from Marylebone to Banbury. Thales, as successors to Alcatel, supplied new equipment and Atkins designed and installed the inductive loops, which included lengthening some existing loops to comply with the required standard

As co-sponsors, Chiltern Railway and Network Rail staff have been engaged in the supervision and monitoring of the overall project.

Impact of the Blockades

Having to close a line to carry out work is disruptive and Chiltern Railways have been very careful to minimise inconvenience to the public. During the Neasden works, passengers for the Amersham / Aylesbury line had to change at Harrow and use the LU Metropolitan Line service.

A Chiltern service from Bicester and High Wycombe operated to Paddington with First Great Western cancelling their Paddington Greenford service so as to provide sufficient capacity between Old Oak Common and Paddington. Birmingham trains were diverted to Didcot with passengers changing to FGW to reach London.

The Wembley to Princes Risborough possession required an element of bus substitution with passengers for the High Wycombe area using buses from Amersham, and those for Bicester being provided with a bus service from the new Aylesbury Vale station.

Passengers at stations in the inner London area had a choice of substitute buses or local LU services.

The pain was relatively short and with many people on holiday, the Chiltern management took the view that a ‘big bang’ approach with sensible use of blockades was preferable to even more weekend closures.

Bicester North. Photo: the rail engineer.

The Achievement and the Future

With all work being completed by 30 August, Chiltern Railways had a week to learn how to use the revised layout before introducing its new timetable on September 5th.

This gave a 100mph capability over most of the route enabling a fastest time from Marylebone to Birmingham of 90 minutes with two intermediate stops, at Solihull and Warwick Parkway. Every hour a service runs with a 100 minute schedule with additional stops at Leamington Spa and Banbury.

That is nearly as quick as the WCML and perhaps more convenient for the sizeable populations of towns along the route.

Evergreen 4?

This part of Evergreen 3 is however not the end of the story. Part 2 of the project will provide the much publicised new chord at Bicester, a new parkway station for north Oxford at Water Eaton Parkway and an alternative service from London to Oxford, also providing journey opportunities between High Wycombe, Bicester and Oxford.

The ministerial go-ahead of the scheme is expected by the end of 2011 with design and construction work taking place in 2012/3 and the new service being in operation from 2014.

This will be another story and the rail engineer looks forward to following its progress.


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