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. Since 1989, rail services have been run using units, which, prior to this, had been used on the London Underground's 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 will be two-car trains built using the existing bodyshells and bogies of former London UndergroundD78 stock units modified for use on the National Rail network. These will 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, 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, but due to the COVID-19 pandemic, the first unit is now due to be delivered for testing in September 2020.
