The British Rail Class 450 Desiro are third-rail DC electric multiple unit (EMU) passenger trains that entered service during 2003. Used for outer-suburban services, they were built with both first- and standard-class accommodation. They have a maximum speed of . The Desiro UK family also includes units of Classes 185, 350, 360, 380 and 444. Along with the Class 444 Desiro, the Class 450 units are operated by South Western franchise operator South Western Railway. Introduction In April 2001, 785 vehicles were ordered by South West Trains in order to complete the replacement of its slam-door rolling stock, in accordance with its franchise commitment to do so by 2005, as the slam-door trains, many of which were more than 40 years old, did not meet modern health and safety requirements. Introduction to service was delayed by the required power supply upgrades capable of powering the new trains, which feature air conditioning, a feature not present in the slam-door trains they replaced. In the December 2004 timetable change, the Class 450 Desiro began serving most intended routes, although introduction was delayed until June 2005 in some areas. The units are leased by Angel Trains to South West Trains. Sixty-eight new vehicles were ordered by South West Trains as a replacement to the growth order which was diverted to form the similar range of electric multiple units. Operations Class 450 units operate suburban, outer-suburban, and regional services from London Waterloo. They are used on all SWR lines except the West of England Main Line and the Eastleigh to Romsey Line. On occasion Class 450 units are also used on the Portsmouth Direct Line for services between Waterloo and Portsmouth Harbour, in place of the intended Class 444. The difference in comfortparticularly the higher-density 2+3 seating arrangement used on the Class 450 fleethas prompted complaints from some passengers affected by the substitution. Both the Class 444 and 450 fleets are maintained at the purpose-built Northam Traincare Facility in Southampton, which is equipped to perform both preventative and corrective maintenance, deep-cleaning, and overhauls on up to eight units simultaneously. Class 450/2 and more orders Originally, SWT's order with Siemens was for 100 four-car sets (the current 450/0) and 32 five-car sets, intended as Class 450/2 for inner-suburban use. The Strategic Rail Authority, however, did not agree to the terms required, such as the lengthening of platforms and changes to railway infrastructure. As a result,