Commuters in Melbourne are bracing for four years of gridlock around Flinders Street Station as a major lane closure begins.

One of three lanes on Flinders Street westbound has been closed between Russell Street and Swanston Street because of construction work for the Metro Tunnel project.

It means motorists trying to turn left onto St Kilda Road will now only have one lane instead of two.

Motorist will now only have one left lane to turn onto St Kilda Road. (Nine)

The Metro Tunnel project is expected to cost $11 billion. (Metro Tunnel Victoria)

The lane reduction will be in place for the next four years.

Commuters are being urged to give themselves about 15 extra minutes while travelling through the area.

The closure will allow space for works on the new Town Hall station at Federation Square.

New train stations around the CBD will make commuting easier around Melbourne.

Read more: Thousands of human teeth discovered during Metro Tunnel works

The Melbourne Visitor Centre, in Federation Square, will be torn down so a 18m high acoustic shed can be built.