Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Croydon testbed Croydon

Tramlink is one of several light rail projects set to transform UK urban transport.

Trams are in vogue. Rapid transit and good integration with existing traffic infrastructures, low environmental impact and high returns on private-sector investment represent a win-win recipe for mobility in Britain's car-clogged cities.

The new generation of light rail systems is likely to be PFI funded, privately owned, and run with the blessing of local councils and planners. They will fill gaps in existing public transport networks and will be designed to provide a viable alternative to travel by car. There are currently 10 light rail systems on the drawing board for the UK with construction of Croydon Tramlink now well advanced.

The Croydon system builds on lessons learned from Manchester and Sheffield, which pioneered the reintroduction of tram transport in the early 90s: it will not, for instance, run in deregulated competition with bus services. Rather, it will be operated as a principal service by London bus company CentreWest Buses. In Croydon, trams will be the kings of the road - markings and signalling will give them priority over other users. They will be fast and frequent.

'Good business attracts institutional investors,' says Dapo Obatusin, financial expert at Croydon concession company Tramlink Croydon Ltd. TCL is a design-build-operate consortium made up of CentreWest (a subsidiary of FirstBus), Austrian tram builder Bombardier, Amey-McAlpine Construction Joint Venture, and investors Royal Bank of Scotland and 3i have together put £75M into the £200M scheme. Experience won in PFI roads concessions was applied by the consortium to pre-bid analysis of Croydon Tramlink. Amey's private finance unit director Charles Mogg says it was clear from the outset that the system was a 'robust investment. Light rail concessions represent an opportunity to see a financial up-side. It's all about generating revenue.'

Greater Manchester Passenger Transport Executive estimates that the Metrolink, in operation since 1992, is between 60%-70% more efficient and contributes 66% less particle emissions per passenger mile than cars. It has cut car journeys made in Manchester by 2.5M a year. Croydon will equal or better these statistics.

'Trams are a big city transport solution,' says Obatusin. This is echoed by the Amey-McAlpine construction joint venture (CJV) and design sub-contractor, consulting engineer Gibb. Gibb assistant project manager Roger Jones points out that, in terms of population, commercial activity and relationship to national road, rail and air connections, 'Croydon is a self-standing town'. With a loop encircling the town centre, the three branches will intersect with and connect London Underground's District line and seven main-line rail stations.

It also links Croydon centre with significant suburban 'nodes' at Wimbledon and Mitcham Junction to the west, Birkbeck and Beckenham Junction to the north-east, and Addington village and New Addington to the south-east. The system will establish Croydon as a regional transport hub and, with 38 stops along its 28km, it is geared towards providing a high degree of local service.

Taking people where they want to go is seen as a significant factor in making the scheme a success. Public consultation carried out in 1991 helped establish the Tramlink route approved by Act of Parliament in 1994. Trams will run to a timetable, providing a secure service, and fares will be priced in line with LRT norms.

Journey times are forecast to be less than half those of buses. Disused heavy rail routes account for 18km of the Tramlink route, and the service has priority on sections of road shared with other vehicles. Jones says: 'High quality service makes it more attractive than buses, which carry a distinct social stigma.' Its agility and local relevance, he adds, are 'the carrot factor necessary to get people out of their cars'. And TCL and the Government, which has granted a £125M subsidy, are both confident that out of their cars and onto trams people will get. Obatusin says: 'Tram systems are increasingly popular in the UK because they offer a high capacity for moving people'.

TCL has a 99-year concession agreement divided into two phases: design/build and operation. CJV will handle maintenance once construction is complete, and the system goes into operation in November 1999.

Tram systems are well established in a number of European cities, and CJV has drawn on tried and tested overhead power supply and signalling systems. Drivers will obey normal highway regulations. Stations, by Gibb's in-house architects, are simple, designed to offer easy access, weather protection, and to have low environmental impact. Platforms are flush with the tram-deck and - to assist passengers with impaired sight - have textured paving to denote where tram doors are.

Putting a tram route into an urban environment that is ostensibly 'full' has been a greater challenge, and Gibb has paid close attention to making boarding and disembarkation points easy for pedestrians to access.

According to Gibb project manager Glenn Player, the single most important element - and the most technically sophisticated - is the track slab itself. It has been purpose-designed for the Tramlink to perform a number of functions:

Because track replacement will be very disruptive in Croydon's busy streets, track has been designed for longevity. In a reversal of heavy rail norms, wear is transferred to the wheels of the tram. This is particularly evident at bends, where the gap locating the wheel flange widens. Up to 30mm wear can be tolerated, and of the 24 trams ordered for Tramlink, three will be out of service at any time, allowing CentreWest to carry out major maintenance.

To minimise shock and wheel noise as trams pass through residential areas, a modified polymer bitumen track mounting has been developed. The mounting also serves to isolate the track from the surrounding ground. Track provides a return path for the electrical current, and service providers - particularly electrical and telecoms - were concerned that electro-magnetic interference could affect them. Jones says the pre-cast slab works like a Faraday cage.

Over all, CJV project director Gerry Barnett comments that design and construction has been characterised by tight time pressures and the logistical problems of integrating the tram network physically.

The project is fast-track and in order to meet planning cycles, Gibb designed the £135M infrastructure in nine months. Regular revision has been required following discussion and negotiation with utilities companies - which have a legal right of protection, with Railtrack, from which TCL leases part of the Tramlink route and which has 'grandfather rights' - and with the three borough councils involved in the scheme. Player says the project has been 'a constantly evolving programme. The emphasis shifts around as different parts of the scheme move forwards or are halted for approval. There is a lot of overlap.'

In order to minimise disruption to other services and day-to-day life in Croydon, it has also been necessary to fit work into tight time frames. On a section running next to Railtrack line on the Beckenham branch, CJV had a window of only 16 days to carry out work.

Two bridges, at Mitcham and Wandle Park, cross train tracks. Work took place overnight and had to be scheduled 18 months in advance. The choice of design - each consists of five parallel pre-tensioned, pre-cast beams - was selected because it allowed rapid erection and required minimal advance site preparation.

Though simple in design, the bridge at Mitcham is skewed at 60 degrees, giving it a relatively large 20m span. At Wandle Park, a steep incline followed by a tight bend was required to negotiate a difficult alignment.

The double-section trams to be supplied by Bombardier have closely grouped wheels which gives them a compact turning circle. However, this produces pronounced end- and centre-throw. The safety margins required to accommodate the large kinematic envelope by Her Majesty's Railways Inspectorate, which is regulating work on the Tramlink, have been one of the most universally challenging criteria to satisfy. For example, new safety guidelines have increased the minimum tolerances required on sections where the embankments are shared with heavy rail.

For financial and environmental reasons, CJV was required to keep any alterations needed along its route to a minimum. On the New Addington branch, however, there was added cost, where the link dodged protected trees and badger-sets.

This serves to point up further the green mind-shift away from car culture. Mogg points out that PFI cut its teeth on roads projects in the early 90s; it is significant that public transport systems are now a sound investment. Barnett, meanwhile, says for Amey: 'It's fairly obvious that spending on roads has declined, and a company that wants to maintain its vitality has to diversify. We see light rail as a growth market.'

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.

Related Jobs