INTRO: The original Docklands Light Railway cost £77m, but Richard Hope found that total investment is approaching £1bn as a third extension nears completion - and there is more to come
BYLINE: Ian Brown
Chief ExecutiveDocklands Light Railway Ltd
BYLINE: Bill Shepherd
Project ManagerLewisham ExtensionLRG Contractors
CHRISTMAS WAS DUE to see a major software upgrade on the Docklands Light Railway that will allow more trains to operate on London’s 22 km automated network. A weekend closure on November 21-22 demonstrated to HM Railway Inspectorate that the second generation software functioned satisfactorily, and DLR Ltd Chief Executive Ian Brown promises that ’it will unlock a lot more capacity which is badly needed’.
DLR has had a chequered and often troublesome history. Its purpose was to improve access to huge areas of derelict land surrounding London’s docks, which were seen as ripe for redevelopment when containerisation and bigger ships triggered a migration down-river to Tilbury by the Port of London Authority.
Bids were invited in 1984 for a 12·1 km fully automated mini-metro to be built and equipped at a fixed price of £77m. This rock-bottom price was made possible - but only just - by routing much of the line on or beside closed and active railways. Light rail standards were adopted for grades and curves, if not for train control. While the 6% ruling gradient is still valid, the time wasted in negotiating 40m radius curves through junctions at 20 km/h has since been regretted. The minimum radius was increased to 100 m for the latest extension and this will remain the aim for future developments.
Demand explodes
No sooner was DLR under construction than the massive office development at Canary Wharf took off. Long before it opened on August 31 1987, a major capacity upgrade and a 1·6 km extension in tunnel costing £276m to Bank in the financial heart of the City of London was on the drawing board. The tunnelling contract was actually awarded on July 17 1987.
The bankruptcy of Olympia & York - the developer of Canary Wharf - coupled with an economic downturn which hit white collar jobs in the financial sector particularly hard, had actually brought some much needed relief to the hard-pressed DLR by the time the Bank extension opened in 1991. Even so, 34000 passengers a day were being carried by a railway that was specified for a peak loading of 1500 passengers/h in one direction, equating to 22000 passengers per weekday.
Meanwhile, a major upgrade was in progress. More rolling stock meant lengthening station platforms, and because the original train control system was clearly not up to the job, Alcatel was contracted to replace it completely with Seltrac, as used on Vancouver’s Skytrain. For several years, DLR was closed after 21.00 and all weekend to enable this work to continue; it included a total rebuild of Canary Wharf and West India Quay stations.
As planned, the original DLR consisted of an east - west line from Tower Gateway to Beckton interchanging at Poplar with a north - south line from Stratford to Island Gardens, but the 8·4 km Beckton leg was deferred.
By the time Beckton finally opened on March 28 1994 at a cost of £280m, the property market had collapsed and the north side of the Royal docks which it was built to serve was still a wasteland.
As Brown puts it, ’there was a rather pregnant pause without anything happening’. Not helping was the fact that the Beckton line was equipped with Seltrac well before it was deemed reliable enough to retrofit the original network, so a Beckton - Bank journey meant changing twice.
Franchising
While Beckton languished, weekday demand had jumped to 50000 passengers by 1995, and then ramped steeply to over 100000 by last autumn with the rate of increase tending, if anything, to get steeper. Passenger numbers have increased from 8·3 million in 1993-94 to a forecast 26 million for 1998-99.
Meanwhile, operation of the DLR was franchised for 7 years to Docklands Railway Management Ltd, a consortium of Serco and DLR managers. Commencing on April 6 1997, this was the last rail franchise to be let before the change of government on May 1, the franchising of British Rail’s passenger services having been completed in March.
Brown explains that there are now three organisations responsible for DLR. His company, Docklands Light Railway Ltd with a staff of 20, manages the DRML franchise as well as the concession awarded to City Greenwich Lewisham Rail Link plc for building and maintaining the Lewisham extension (opposite).
Since the winding up of the London Docklands Development Corp last April, responsibility for DLR has reverted to the Department of the Environment, Transport & the Regions. Oddly, Brown reports to the minister responsible for regional regeneration, Richard Caborn, rather than the transport minister, John Reid. Despite this, Brown points out that ’there have been a series of initiatives to integrate DLR with other public transport, notably bus services.’
Out of a total grant of £17m in 1997-98 paid to DLR, DRML will receive an operating subsidy of less than £4m in 1998-99, compared with revenues of some £20m. The rest is to fund upgrades and development.
Ownership of all the assets remains with DLR Ltd in the public sector. DRML must operate and maintain trains, stations and infrastructure to a tight specification, meeting performance targets which get higher each year.
Brown says ’the franchisee has delivered on all the targets except for the availability of lifts and escalators during three accounting periods, so the formula has worked against a background of fantastically growing business.’ He identifies the reasons as ’a working population that is growing like mad and improved service reliability.’
In preparation for the Lewisham extension, which will be worked by the existing fleet of 70 six-axle articulated cars that mostly run in pairs, this fleet is being re-engineered with new traction motors, tachogenerators for the ATO, and dampers.
The other weakness is the moving block train control system which Brown characterises as ’very susceptible to overload in terms of the number of trains on the network.’ The software upgrade costing £12m which was due to be commissioned over Christmas ’should crack this problem and give us a lot more capacity - which we badly need.’
Alas, there have been too many disappointments in this area to be certain of success until it has been proved in revenue service.
JLE uncertainty
Given that the software works, DLR faces one major problem above all others during the course of this year: the on-going delays in completing the Jubilee line extension. This high capacity Underground line was due to open in March 1998, but is now expected to open in stages during 1999.
JLE was expected to take 40% of DLR’s traffic when it opened throughout. As soon as the Lewisham extension opens, some 5000 commuters are expected to transfer immediately to DLR with steady growth thereafter as travel patterns adjust.
While JLE completion is still expected ahead of the Lewisham opening, the gap has narrowed alarmingly. Brown and DRML are therefore ’bringing forward contingency plans to put more trains on the railway’. In addition, some seats will be removed from 20 of the 70 cars. From April, one of them will be included in every train leaving Bank in the peak hours, lifting capacity on this critical section by 10%.
Brown is also looking to buy another 12 to 18 cars similar to those already in service - thus side-stepping safety case issues which plague the introduction of new electrically powered trains in Britain.
The intention when Lewisham opens is to have 15 departures per hour running alternately to Bank and Stratford, plus 5/h from Beckton to Tower Gateway. Lewisham will be stepped up to 20/h as traffic builds, and another 5/h will be added between Bank and City Airport when that line is completed around 2002-03.
CAPTION: A row of BN-built B90 and B92 trainsets waits for the rush hour at Beckton depot
CAPTION: The rapid increase in DLR ridership was sparked by the office development at Canary Wharf
CAPTION: The Lewisham extension follows Deptford Creek to squeeze through congested suburbs
TABLE: DLR traffic
million journeys
1987-88 3·3
1988-89 6·6
1989-90 8·5
1990-91 8·0
1991-92 7·9
1992-93 6·9
1993-94 8·3
1994-95 11·5
1995-96 14·5
1996-97 16·7
1997-98 21·4
1998-99 26·0*
* estimated
International links
DOCKLANDS Light Railway has two further extensions at the planning stage, both of interest to international travellers.
In June 1998, the Deputy Prime Minister, John Prescott, whose brief includes DLR, approved in principle a 1·5 km branch from Prince Regent to London City Airport, the smallest of five which serve London.
Howard Smith, Planning & Development Director of DLR Ltd, says the double-track elevated route - which will include a lifting or swing bridge for vessels passing through the docks - has been provisionally costed at £35m. ’Consultants W S Atkins are doing a post-feasibility study of engineering options, but we don’t want to design it down to the last nut and bolt.’
This is because the government would like the project to be funded and built under a concession in the same way as the Lewisham extension. ’We are going through the procurement process this year, which will include an intensive market testing stage’, says Smith. ’The intention is to bring a partner on board at the earliest possible stage.’
Consultation with local businesses and residents will start soon with a view to applying for a Transport & Works order as early as August. Smith believes ’we have a design with very low impact that brings real benefits to local residents’, and hopes it might be possible to avoid a public inquiry. If so, ’we could start building in 2000 and opening in 2002 is a possibility - but a public inquiry would add 18 months to that timescale.’
The airport station will be designed for through running in case a decision is taken to extend the branch, possibly under the Thames to Woolwich and Thamesmead, a large post-war residential development with poor public transport links.
The other extension, currently at the engineering feasibility stage, would be from Stratford station to the proposed Stratford International station on the Channel Tunnel Rail Link, which is about 500m away.
Smith says there are actually three traffic objectives, the third being proposed office and residential development ’which could well be more important to us than either of the two stations.’ Hence there could be one, two or even three DLR stations serving the area. DLR could also replace the proposed travolator link between the main line and CTRL stations ’which would be very expensive.’
The problem is that DLR must cross over or under the multi-track Great Eastern main line, and its path is strewn with obstacles. ’Although CTRL does not open until 2007, we have been asked to go back to government with our ideas by April.’
Under the Thames to Lewisham
IN CONTRAST to the delays and cost over-runs which have dogged London Underground’s Jubilee Line extension to Canary Wharf and Stratford, construction of DLR’s 4·2 km southern extension to Lewisham has gone smoothly.
Boring of the 1080m long twin tunnels under the River Thames from Island Gardens to Railtrack’s Greenwich station was finished in April 1998 - four months ahead of schedule - and civil works were substantially complete by the autumn of 1998. Project Manager Bill Shepherd expects test trains to start running in March. The extension is now expected to open for revenue service ahead of the January 2000 contract date, in time for the Millenium celebrations.
Work commenced in October 1996 after a 24 1/2 year concession tendered under the Private Finance Initiative was signed by City Greenwich Lewisham Rail Link plc. CGL Rail members - John Mowlem & Co, Hyder, London Electricity and Mitsui & Co Ltd - are committed to financing and building the £200m project, apart from certain grants, and then maintaining it during the life of the concession.
LRG Contractors in charge of construction is a joint venture of John Mowlem and Mitsui-Nishimatsu, the latter responsible for boring the tunnels. Electrical work is subcontracted to London Electricity Contracting Ltd, and train control to Alcatel Canada Inc which installed the Seltrac automatic train operation system on the rest of DLR.
Under the river
The new line diverges from the present Island Gardens branch north of Mudchute and drops into a relocated station in cutting. It then runs in cut-and-cover under Millwall Park to a new underground station at Island Gardens. The viaducts at Mudchute and Island Gardens built as part of the original DLR are to be demolished, although the Grade II listed Great Eastern Railway brick viaduct across Millwall Park will remain.
The new Island Gardens station box includes the chamber from which Nishimatsu’s tunnel boring machine was launched for the first drive in May 1997. It will house ventilation plant installed primarily to control smoke in the event of a tunnel fire; matching fans are being installed south of the river crossing at Cutty Sark station.
A single TBM was used to drive each running tunnel in turn, starting twice from Millwall Park. Because it had to bore through water-bearing sand and gravel under the tidal river, a full-face pressurised slurry TBM was supplied by Markham of Chesterfield. Excavated spoil was mixed with the slurry and piped to the surface, where the slurry was separated for re-use.
Finished diameter within the six reinforced concrete segments forming each 1·2m wide ring is 5·2m, larger than DLR’s tunnel to Bank because of a requirement by the Health & Safety Executive to provide a more generous evacuation walkway, and also low-level access from the opposite side for effecting repairs or jacking a derailed train. One cross-passage halfway between Cutty Sark and Island Gardens links the evacuation walkways in adjacent tunnels.
At Cutty Sark station, named after the famous sailing ship on display here, the rails are 19 m below ground barely 100m from the river. Diaphragm walls 28 m deep were excavated using bentonite slurry to support the soft ground. On its first passage the TBM then cut through both end walls, using its cutter teeth to remove concrete which had been left unreinforced over the affected area, creating a 5·2m diameter lined tunnel through the incomplete box.
The box was then excavated using the top-down method. Once the running tunnel had been exposed, the rings were unbolted from inside and removed. By the time the TBM arrived on its second pass, the box had been fully excavated and the bottom slab cast so the 180 tonne machine could be jacked through.
The bored tunnel runs into cut-and-cover beneath the ’Up’ platform at Railtrack’s Greenwich station, avoiding the listed station building; once the terminus of the London & Greenwich Railway, it was dismantled and relocated when that line was extended.
The line rises until the tracks are at the same level as the London - Dartford line, where the DLR platforms are located to give convenient interchange with Connex South Eastern trains. The line then climbs on to a 786m concrete viaduct of 20 spans which winds above the tidal Deptford Creek. Over the water the post-tensioned concrete deck was cast in-situ in sections by the balanced cantilever method because of the limited access from below.
On the viaduct the minimum curve radius of 100m was needed to ’wiggle’ the alignment between the buildings of Lewisham College to reach Deptford Bridge station which spans the A2 trunk road. The line then descends to ground level following the Ravensbourne river, which has been diverted in places. The contract includes the landscaping of parkland through which the river now runs in a natural bed rather than the previous ugly concrete-lined channel.
After one more stop, the line terminates in the Vee formed by two more Connex South Eastern commuter routes (above). Jacking was used to slide three concrete boxes under both pairs of tracks and platforms, to form a running tunnel and two passenger interchange subways. Connex will move its booking office into the new station complex, which will also offer good interchange with over 30 bus routes that serve this focal point.
Noise prevention
Tracklaying is almost complete above ground, and is currently in progress through the tunnels. The 80A flat-bottom rail is secured by Pandrol clips to presstressed concrete sleepers on ballasted sections.
Where the track is on structures or in tunnel, baseplates rest on resilient pads up to 30mm thick bolted to a cast in-situ concrete slab. Where the bored tunnels pass under the town of Greenwich, these slabs float on steel springs to reduce ground-borne noise and vibrations (left).
To avoid difficulties which have been experienced in replacing rubber pads under floating slabs, these springs are housed in steel cylinders cast in the track slab. A cover plate flush with the top surface of the slab is then secured in place. Removal of this plate allows the springs to be inspected easily, and they can readily be replaced using special tools without disturbing the slab.
The safety specification requires check rails or other measures to constrain derailed vehicles wherever the line is in tunnel, on an elevated structure or on retained earth structures. Check rails on independent baseplates will be laid throughout the tunnels, but above ground derailment constraint is provided by a heavily reinforced upstand, or curb, along the outside of each track slab. n
