More than a third of Melbourne's tram routes will be forced to run a different course through the city during the long period of disruption while Swanston Street is dug up to build the Melbourne Metro rail tunnel.

Ten tram routes that currently run along Swanston Street will be diverted onto other lines in the CBD's west end, requiring the construction of new tram tracks in the city centre, as the $11 billion rail tunnel is constructed.

Trams will continue to run along Swanston St during construction of the Melbourne Metro Rail project. Credit:Jesse Marlow

Instead they will run on Elizabeth Street, William Street or Spencer Street.

This will require building a new connection between the Elizabeth Street tram terminus and Flinders Street's tracks to maintain the connection to St Kilda Road.