Commuter chaos in the downtown core is set to reach a new level Monday morning as the eastbound ramp from the Gardiner Expressway to York, Bay and Yonge streets permanently closed at 5 a.m..

The ramp is one of the most used off-ramps.

As CityNews first reported back in February, the ramp is set to be replaced with a shorter one from the eastbound Gardiner to Lower Simcoe Street, but that is not slated to open until January 2018.

Harbour Street will eventually be widened to four lanes from Lower Simcoe to Bay Street as part of the project in order to accommodate the additional traffic. It will also improve pedestrian and bicycle access to the waterfront.

During construction, Harbour will be reduced to two lanes of traffic in the area and there will be periodic closures of the centre lane on the street from Lower Simcoe to Bay street between May 1 and June 15.

According to the city, more than 4,500 vehicles travel the eastbound Gardiner from Jameson Avenue to the core every hour during the morning rush and 3,300 of them use the York-Bay-Yonge off ramp.

Motorists will be able to access the downtown area by exiting the eastbound Gardiner at the Jameson, Spadina Avenue and Jarvis Street exit ramps. From April 10 onward, eastbound Lakeshore Boulevard will be accessible from the eastbound Gardiner at Spadina.

Traffic signal timing on alternate routes will also be adjusted to minimize congestion but motorists should expect delays.

Work on the project is expected to take place Monday through Saturday from 7 a.m. to 7 p.m. and overnight work will take place on the weekends.