Flinders Street will be jammed with traffic for up to four years owing to works on the Metro Tunnel.
One of the three westbound lanes between Russell and Swanston streets was shut from 5am today.
The lane closure means motorists seeking to turn left down St Kilda Rd will only have one lane, and those travelling to the city’s west a single lane to drive ahead.
The squeeze is expected to create a significant bottleneck for the thousands of cars that use Princes Bridge to cross the Yarra River, and those travelling down Russell St.
Commuters are warned to allow an extra 15 minutes for their journey.
The closure, to last up to four years, will allow major works on the new Town Hall station at Federation Square. The Melbourne Visitor Centre will be torn down this week to make way for a giant acoustic shed.
The acoustic shed will be 18m high.
The around-the-clock construction work is to build the Metro Tunnel and the underground train platforms.
A pedestrian tunnel will also be built to connect the new underground Town Hall station to Flinders St Station and the City Loop.
Plans to demolish the Melbourne Visitor Centre hit a roadblock when Heritage Victoria ordered that no work could begin on the square without explicit permission.
But authorities won a special permit for the work and will begin the demolition within the week.
Public Transport Minister Jacinta Allan said: “By freeing up the City Loop, space will be created on the network for more than half a million extra peak passengers every week.
“We know this is going to cause lots of disruption for commuters, and we thank them for their patience.”
The road closures come as work on the $11 billion Metro Tunnel project ramps up. Detailed final designs for the five new underground stations have been released.
St Kilda Rd has become another traffic bottleneck. Its narrowing to one lane between Dorcas St and Toorak Rd West, to allow for work on Anzac Station will last years.
VicRoads data has revealed that since the closures came into effect, some Melbourne motorists were spending an extra 22 minutes on the road on their way home.
Meanwhile, VicRoads is warning drivers to expect delays along Punt Rd, Swan St and Olympic Boulevard overnight and on Wednesday as lanes are closed for works on the state’s first continuous flow intersection.
Speed and lane restrictions will be in place at the Swan St and Punt Rd intersection overnight between 8.30pm and 5.30am, while outbound lanes will be closed on Olympic Boulevard approaching Punt Rd between 7am and 2.30pm on Wednesday.
Work on the intersection will continue until late 2019.