Commuters will save up to 25 minutes on their journey to the inner-city once the $11 billion Metro Tunnel is built, the state government promises.

For the first time, the Andrews government has released modelling showing the time commuters will save when the Metro Tunnel creates an alternative route through the CBD and allows more services through the City Loop.

The design for the new Town Hall station on the Metro Tunnel.

Six months out from the November state election, the Premier was spruiking the time savings on Wednesday ahead of excavation works on the new Anzac Station, near the Shrine of Remembrance.

Premier Daniel Andrews said many people would save time on their commute, because they would no longer have to catch a train into the CBD and then get a tram, or walk, to reach Parkville or St Kilda Road.