British Rail Class 484

The British Rail Class 484 is a class of electric multiple unit which are being built by rolling stock manufacturer Vivarail for the Island Line on the Isle of Wight. The units are converted from London Underground D78 Stock, originally manufactured in the late 1970s and early 1980s by Metro-Cammell.
Five units are being converted for the Island Line to replace the Class 483 sets, with the first delivered for testing in 2020. The line is currently closed (January 2021) and was originally scheduled to reopen on 1 April 2021 with the new fleet of trains, but delays to the required infrastructure work as a result of the COVID-19 pandemic have extended the shutdown period by six weeks to 13 May 2021, and problems with software on the trains have delayed their introduction until later in the year.
History.
The Island Line, an long rail route on the Isle of Wight between Ryde and Shanklin, has historically been limited in the type of rolling stock that can be operated due to clearance levels, particularly in the Ryde Tunnel between and . 
This continued even after electrification in 1966. The Island Line has used repurposed former London Underground stock since electrification; British Rail Classes 485 and 486, built as 1923 tube stock, were used from 1966 to 1989. Since 1989, rail services have been run using units, which originated as 1938 tube stock and last ran on the Northern line. 
However, these units were first introduced on the Underground in 1938 and, by 2019, were more than eighty years old. This made them increasingly difficult to maintain, with the original fleet of eight eventually reduced to four in service, with another two retained as spares donors. As a consequence, replacement of the rolling stock became an urgent priority - this requirement was eventually linked with a wider need to invest in improvements in the line itself, and saw suggestions that it might be converted to a light rail operation, or even a bus rapid transit route.
However, in 2019, it was announced that the existing third rail operation would be retained, with a total of £26m invested to make improvements. A significant proportion of this would be used on the procurement of a fleet of new trains, which it was announced would be sourced from Vivarail's D-Train platform.
Trains.
The Class 484 units are two-car trains built using the existing bodyshells and bogies of former London Underground D78 stock units modified for use on the National Rail network. These have similar features to the trains from the same family, with wi-fi, power sockets and CCTV. The D78 Stock is similar in terms of height to other National Rail rolling stock in Great Britain and taller than the previous Class 483, but having undertaken a survey of the route, Vivarail confirmed that its proposed units were capable of traversing the Ryde Tunnel.
Gauging trials had previously taken place in the 1960s to determine whether units were suitable for use on the route. The first of the total of five units was due to be delivered for testing in the summer of 2020. The first unit arrived on the Isle of Wight on 19 November 2020 via ferry.
Fleet details.
Each unit is formed of 2 former London Underground D78 Driving Motors, with cars 13* facing Ryde Pier head and cars 23* facing Shanklin. 