Following the announcement that it was the preferred bidder for the renewal of the South West Trains franchise, on 23 April 2001 Stagecoach placed what was then the largest single order from the UK for new trains and associated services. Perhaps in part due to its unsatisfactory experience with the introduction of its fleet of class 458 Juniper EMUs, the order was not placed with an engineering conglomerate with manufacturing capacity in Britain but went to Siemens Transportation Systems of Germany and Austria. Prior to this Siemens' only penetration into the British market had been with the class 332 EMUs for Heathrow Express and class 333 EMUs for Northern Spirit/Arriva Trains Northern's West Yorkshire services. These two classes are noted for their relatively pain-free introduction to service and reliability. The overall order was for £1 billion, consisting of £640 million for 785 vehicles (to replace SWT's entire slam door EMU fleet) and the balance for service and maintenance of the fleet for the duration of the contract, plus an option for placing a second order. Angel Trains is providing funding. The rolling stock order was originally for one hundred 20 metre 4 car sets for outer suburban service (with a planned delivery between November 2002 and October 2003), thirty two 20 metre 5 car sets for suburban service (planned for delivery between October 2003 and February 2004), and forty five class 444 23 metre 5 car sets for mainline use (planned for delivery between February and September 2004). The 23 metre units will not be covered in this section. Towards the end of 2003 the order for the 5 car 450s was cancelled as the SRA would not support changes to suburban infrastructure to allow 10 car trains (platform lengthening, etc). A further ten 4 car units for SWT were substituted taking the total number of the 450/0 class to 110. The SRA took over the balance of this order to provide 30 Class 350/1 4 car 25kV ac EMUs for use on the southern end of the West Coast mainline. These units will work from a pool Silverlink County, Central and Virgin services so will not carry any TOC livery or brandings. Their superior acceleration will allow better use of paths on a demanding part of the railway network.

photograph by Paul Emery

These vehicles come from Siemens' Desiro range, a family of multiple unit trains of flexible modular construction which are capable of electric or diesel-electric, diesel-hydraulic or diesel-mechanical propulsion. Examples of Desiro units are already in service in Germany, Greece and Slovenia. Being of modular design they are constructed from pre-fabricated sub-assemblies and meet the latest safety and disabled access requirements. Gangwayed and non-gangwayed versions are possible. Self-supporting aluminium extrusions are utilised in the welded construction which also provide "T" section strips on the inside to which interior fittings and components are bolted. Sliding plug doors at one third and two third positions are provided on this particular series of Desiro and SWT has selected gangways throughout.

photograph by Paul Emery

Each unit has four 1TB2016-0GB02 asynchronous traction motors. The bogies are of the steel mainframe SGP SF5000 type with the primary suspension being of coiled springs, secondary being supplied by air bags. Dellner couplers are fitted at unit ends. Traction equipment is mounted in resilient boxes between bogies to reduce the amount of vibration in the passenger saloons. Disc and rheostatic brake systems are fitted and top speed is 100 mph . Resilience is designed into these units improving their availability for service. Non safety critical equipment can be isolated following a failure so the units can remain in use.

photograph by Richard A

The 4 car units, designated class 450/0 (4Des), numbered 450001-450100, are formed DMSO - TCOL - TSO - DMSO, seating 71 - 24 1st, 39 standard, one toilet - 68 - 71 respectively. The 5 car units would have had an additional TSOL and there would not have been any first class accommodation in these units as they were intended only for suburban use. Seating in 1st class is 2+2 and is fitted with a dark blue moquette. Seating in standard class is 3+2, unidirectional and facing, and uses a red moquette. Unusually for suburban and outer suburban units carpet is fitted throughout. The interior finish of these units has been described as being to an extremely high and robust standard. The 450/0 units feature a new SWT "outer suburban" livery designed by Ray Stenning of Best Impressions, the design house responsible for the previous - now considered "mainline" - livery used on classes 442, 159 and (now incongruously) 458. Light blue dots at cantrail level denote first class accommodation - the author of this piece bemoans the lack of standardisation between TOCs, indeed between types of stock within a TOC, on this issue.

photograph by Richard A