Melbourne Metro Tunnel train services will soon begin – but what is the ‘summer start’ and when is the ‘big switch’?

After months of speculation, the Victorian premier has announced the long-awaited Melbourne Metro Tunnel will begin taking passengers in early December.

The Metro Tunnel will connect the Sunbury line in Melbourne’s west to the Cranbourne and Pakenham lines in the south-east via five new underground city stations : Anzac, Arden, Parkville, State Library and Town Hall.

“It is the biggest overhaul of our transport system since the 1980s,” the premier, Jacinta Allan, says.

But trains will only run every 20 minutes during the so-called “summer start” period in December, with commuters having to wait until 1 February for “turn up and go” services.

Here’s what we know about the Metro Tunnel’s phased launch.