It seems like only yesterday since the DLR opened but it was actually back in 1987, with the concept originating in 1984. In the intervening period, the network has seen unprecedented growth that at times has led it almost to become a victim of its own success. So says Martin Collett, the DLR’s Chief Engineer, who gave a fascinating talk to the Institution of Engineering and Technology (IET) recently.

The railway has experienced turbulent times in its short history with many events contributing to it now being a very different network in both size and operation. The last two years has, in particular, seen major upgrading – firstly to cater for increased traffic levels and secondly to be a main carrier of people to and from the Olympic Games. Most of this work is now complete.

Expanding the network

DLR was first built to assist mobility in the creation of the London Docklands area as a business centre. It was effectively conceived as an upmarket tramway with single vehicles operating under automatic control. The original layout was a three-pronged star, with Poplar at its centre, Tower Gateway to the west, Stratford in the north and Island Gardens, on the north bank of the Thames, to the south.

Use of existing railway formations made for low-cost construction over much of the route but the centre section through Canary Wharf involved a new overhead route. It cost £77 million, had 15 stations, and was 13 miles long with 11 vehicles. A fixed block automatic control system was provided by GEC, with a maximum speed of 80kph and a minimum curve radius of 40m. The train service operated as two routes – Tower Gateway to Island Gardens and Stratford to Island Gardens. Although direct running from Tower Gateway to Stratford was possible over the central ‘delta’ triangular junction, the north side was not regularly used. The flat junctions were not then a significant operational restriction.

Whilst Tower Gateway Station was adjacent to Fenchurch Street, it was not in the heart of the City, which was a drawback. To overcome this, the first extension was to Bank via a spur line from west of Shadwell Station in tube-type tunnelling. This was opened in 1991 and cost £149 million. Additional vehicles were acquired for the enhanced service level. Going eastwards, the Beckton extension aimed to serve an area without any form of train service. Opened in 1994 with ten stations either on a viaduct, in cutting and often on a grade, it cost £224 million.

At this time the limiting capacity of the fixed block system became evident and the GEC control system was replaced by the then-new Alcatel (now Thales) Seltrac CBTC system, pioneered on the Vancouver Skytrain. This enabled much closer headways and thus greater throughput. The eastwards extension led to a remodelling of the delta junction so that trains running on the service direct from Tower Gateway to Beckton were grade-separated from the Bank/Stratford-Island Gardens services.

Private funding was used to finance the next extension southwards from Island Gardens to Lewisham in 1999, with a separate company – the City, Greenwich and Lewisham Railway (CGLR) – being created. This involved tunnelling under the Thames with a completely new underground Island Gardens Station and five more south of the river. The cost was £200 million and the line remains a separate legal entity although the systems and operational procedures are fully compatible.

The growth of London City Airport and its lack of public transport facilities was the impetus for the next extension from Canning Town on the Beckton branch. It was initially built to King George V (2005) and then subsequently via a second river crossing to Woolwich Arsenal (2008). Both these extensions, costing £140 million and £180 million respectively, were privately financed by separate companies but the operations and maintenance is fully integrated into the DLR control & communications centre at Poplar. The Woolwich extension needed 2.5km of tunnels under the Thames and all safety verification had to be done under the new ROGS regulations, including the ventilation shafts and ticket barriers.

Two new stations have been built on the existing railway, at Pudding Mill Lane and Langdon Park, both on the Stratford route. The latter is a prototype for a more adventurous architectural style.

Whilst DLR Ltd is the controlling company, operation and maintenance is contracted out to Serco Docklands Ltd (SD) under a franchise agreement. This is competitively tendered but SD was successful in being awarded a renewal in 2009.

The three-car project

Expanding the trains to two vehicles was done fairly soon after opening but the continuing growth in passenger numbers has led DLR to embark on further expansion of train length to three vehicles. Bank and Canary Wharf stations were built with this in mind but most others needed platform extensions. Some of these were relatively easy but many involved expensive civil engineering works to cantilever them out on viaduct sections.

At five stations – Cutty Sark, Elverson Road, Pudding Mill Lane, Gallions Reach and Royal Albert – extending the platforms proved to be uneconomic and selective door opening has had to be introduced. This is done on the basis of having all three cars at the platform but with the first and last doors of the train not opening. This prevents people being trapped in one of the vehicles. The selective door control is automated by use of detectors both at lineside and on the trains but the chosen system is not considered fail-safe. Automatic announcements and emergency walkways are provided just in case doors are incorrectly released.

Tight curvature at South Quay Station prevented the platforms from being extended and the station has been resited eastwards by 200m – a considerable engineering challenge as this section is on a viaduct. The original station had an infamous history, being damaged by an IRA bomb attack on the Docklands area in the 1980s. Tower Gateway Station has a complete new layout designed to separate arriving and departing passenger flows. A single track is sited between two platforms to facilitate this but it does mean that only one train can be accommodated in the station at any one time.

55 new vehicles have been procured for the project, these being built by Bombardier in Europe. The allocation of these has been 22 for the Olympics, six for the Woolwich route, nine for the Stratford International extension and 18 for the Bank-Lewisham service. The new and old types of trains are not electrically compatible so they cannot normally be coupled together. They can however be mechanically coupled for the purposes of recovering a failed vehicle.

The additional trains have demanded an upgrade of the traction power supply together with the low-voltage power for stations, lifts and improved communication facilities. The Seltrac signalling system has been improved to give increased capacity – this has involved changing out the distribution system from a copper cable to a fibre-based network. Some embarrassing failures have occurred during this work with total network shutdown happening on more than one occasion. Reliability has though improved in recent times.

Here and now

Whilst the central delta junction had already achieved a partial grade separation, there remained a flat crossing giving conflict between the Canary Wharf-Stratford and Bank-Lewisham services. DLR has now eliminated this by building a dive under for the latter. This has meant realigning the existing viaduct, it having passed over the Poplar route, to then position it under the Poplar-West India curve. Some spans from the old viaduct were reused to save cost. Because of gradients, the new line no longer calls at West India Quay and is thus only used for peak-hour services. During the day, trains continue to use the flat crossing on the old alignment.

At Canning Town, a more radical remodelling has taken place to eliminate all flat crossings from the four routes that radiate from the station. The work has included connecting in the new route to Stratford International. The layout has been designed to facilitate the arrival of Crossrail platforms in due course.

The ex-BR North London line to North Woolwich was seen to duplicate much of the DLR City Airport line and it has been closed southwards from Canning Town, with the northern section to Stratford Low Level now incorporated into the DLR and extended on to Stratford International Station on the High Speed 1 line. This is now complete but its building has encountered unexpected structural problems, resulting in the project being several months late. The line has five new stations with important interchanges to London Underground and Network Rail at Canning Town, West Ham and Stratford Regional. Private financing was not used but a turnkey contract was let to Skanska/VolkerRail JV for all infrastructure work. Test trains have been running since December and the line will soon open to the public.

The Games challenge

Transporting people to, from and around the Olympic sites is an important element of the planning process. Tickets for the Games will be sold for different sessions and not necessarily for a particular day. DLR happens to serve four Olympic sites, the main ones being Stratford International, Excel and Greenwich. A close liaison has been established with the Olympic Delivery Authority (ODA) to work out the various requirements and situations that may occur.

A special train service will be devised for the Games period which will include transport to and from the opening and closing ceremonies. The timetable must be capable of being flexible enough to allow for event overruns and anything else that might upset timings. Flexibility and resilience of operation will be vital. Any breakdowns must be resolved quickly, be they train failures, traction power disruption or signalling problems. Having huge numbers of people stuck in trains for an hour or more is simply not acceptable.

The numbers and deployment of engineers and technicians will be key, as must be the availability of spares. Lift performance is seen as a major risk. A control & command centre to integrate all modes of engineering and operation is seen as essential. Feeding into this will be all the data associated with passenger handling acquired from ticket machine sales, gate operation and automatic passenger counting machines. Likely surges in flow rates can then be predicted and measures put in place to deal with these as journeys progress. It is not envisaged that a 24-hour service will be required.

The future

Even after the Olympics, there are works being planned that will further expand the operations and catchment area of DLR. These involve –

• extending three-car operation to the Beckton route – already authorised with work underway

• building new operational management offices at Beckton

• creating an extension to the east route from Gallions Reach to Dagenham Dock – work on this had reached an advanced stage before financial constraints within TfL caused a halt, although it is now back in the Mayor’s strategic plans

• double-tracking from Bow Church to Stratford with a new station at Pudding Mill Lane to facilitate Crossrail

• extending the line onwards from Bank in tunnel to either Victoria or Euston/St Pancras – a very ambitious vision but would give much needed relief to the District Line as well as making an interchange with HS2

• heading southwards from Lewisham to Forest Hill to relieve the Jubilee Line

• acquiring additional vehicles to serve the new lines and augment existing train capacity.

DLR has transformed itself in 25 years from a small localised light rail system into a major transport operation in the east of London, serving much more than the Docklands business centre. Its current passenger numbers could only have been dreamed of back in 1984 and this rate of growth continues. The efforts of the DLR’s management and its principal contractors to expand facilities to deal with this growth are commendable but perhaps having a railway that is still local to an area gives that personal sense of ownership and commitment that is so often lacking with bigger organisations.

What the next 25 years will show can only be guessed at but it seems likely that the Docklands Light Railway will be a much bigger affair.

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