TAKING SHAPE at the Siemens works in Krefeld-Uerdingen is a small build of grey EMU cars with orange doors. Quite distinct from the rows of ICE3 and ICE-T cars and ET423 and 425 EMUs for German Railway and VT642 diesel railcars for Romania, they show a marked family resemblance to the Desiro UK units for South West Trains and National Express Group.

The trains are destined to work a half-hourly local service between London’s Heathrow Airport and the UK capital’s western suburbs from July 2005. Managing Director of BAA Rail Vernon Murphy announced on May 6 that this will be marketed as Heathrow Connect, to differentiate it from the existing premium-fare Heathrow Express which links Paddington with the airport every 15min.

Heathrow Express has carried 27 million passengers since its launch, reaching 5 million in 2003. According to Murphy, it now handles 11·5% of arriving and departing air passengers, compared to 14% for London Underground’s Piccadilly Line. Last year it overtook taxis as the leading mode for journeys to and from central London.

A local service to carry airport workers and airline passengers from the western suburbs was proposed in the mid-1990s, but BAA was unable to obtain paths on Railtrack’s busy Great Western Main Line. Replacement of the Thames Trains franchise from April 1 2004 opened up what Murphy called ’a window of opportunity’ to negotiate with the Strategic Rail Authority, Network Rail and incoming franchisee FirstGroup.

Eliminating the present stopping service to Slough will release paths, but the trains must then serve two distinct and overlapping markets. Thus Heathrow Connect has been formed as a joint venture between Heathrow Express Ltd and First Great Western Link.

Between Paddington and Hayes & Harlington the service will act as a suburban train, calling at all stations, and the revenue will go to FirstGroup. Between Ealing Broadway and Heathrow it will provide the airport link. BAA Rail will get the revenue for the final section between Hayes and Heathrow, where a premium fare is envisaged.

Because Heathrow Connect services will not be advertised as through trains and will always be overtaken en route, Murphy believes most London - Heathrow passengers will continue to use the fast trains. There will be no through tickets other than the full Heathrow Express fares.

Due to capacity constraints in the single track tunnel leading to Terminal 4, Connect services will terminate at Heathrow Central. End-to-end journey time will be 25min compared with 15min for the fast trains.

When Terminal 5 opens at the airport in 2008, Heathrow Express services will be diverted to the new terminal, and the Connect trains will be extended to Terminal 4. An extra shuttle will maintain a 15min interval service on the Terminal 4 branch.

In the longer term, Heathrow Connect may be absorbed by Crossrail Line 1, which plans to operate four trains/h into Heathrow Airport from around 2014. BAA Rail is also pushing ahead with the Airtrack project to extend the Terminal 5 branch to carry local services to and from the southwest suburbs.

BAA is investing over £50m in the Connect project, as part of its strategy to improve surface access to Heathrow Airport by public transport. Four 4-car EMUs were ordered from Siemens last year for £23·5m, and another £11·5m is being spent on expansion of the Heathrow Express depot at Old Oak Common. To cope with requirements for Terminal 5, the rolling stock order has now been increased to five 5-car trains, at an extra cost of £15·6m.

The Desiro UK sets have 20m bodyshells compared to the 23m Class 332s used on Heathrow Express. The first four units will be supplied as four-car sets as ordered; following delivery of the fifth train they will each return to Germany to have the extra trailer car added.

The Class 360/2 units are derived from the Great Eastern Class 360/1 sets (RG 11.03 p688), with safety improvements for underground operation, including fireproof seating fabric and low-level lighting strips to signal the route to the emergency exits.

Aluminium bodyshells have been reused from the prototype Class 350 sets developed by Siemens and Angel Trains to launch the Desiro UK concept. These have been stripped to bare metal, and everything else is new, including the complete cab ends.

Each set is formed with two driving motor cars, a pantograph trailer with wheelchair space and a disabled-accessible toilet, and one or two standard trailers. Seating is arranged in a 3+2 layout, providing 266 standard class seats in a four-car set and 74 more in the lengthened units. Two luggage stacks are provided in each car, except the pantograph car which has only one.

The 25 kV traction equipment is the same as the Great Eastern units, with three-phase motors powering the four axles of each driving car. Addition of the fifth car will result in a slight reduction in acceleration, but this will not extend journey times.

The first train is expected to leave Krefeld shortly for commissioning at Wildenrath. One set is also likely to visit the Velim test track in the Czech Republic for high speed trials. Subject to safety case approval, BAA Rail expects to begin trial running in the UK at the beginning of November.

CAPTION: Fitting out of the first batch of Heathrow Connect cars is well advanced at Siemens’ Krefeld plant, although the installation of the Grammer seating (below) has been delayed by problems with the supply of fireproof fabric