A portion of York Street in downtown Toronto will be reduced to one lane in each direction starting Friday to make way for a new extension of the underground PATH network — and it'll be a lengthy shutdown.

The restriction will affect the block of York Street just west of Scotiabank Arena, between Bremner Boulevard and Lake Shore Boulevard West.

The restrictions are expected to last until April 2020, according to the city. The PATH extension is set to open to the public in June 2020, while the city is also replacing some below-grade infrastructure as part of the work.

Once complete, the PATH network, which currently connects more than 75 buildings via underground walkways, will run farther south along York Street, reaching the ICE condominiums at the corner of Lake Shore Boulevard West.

The new branch of the PATH will also create a new walking connection to Union Station.

The city is warning people to expect noise, dust and traffic delays on York Street while construction is underway.

It is recommended that drivers and cyclists use Lower Simcoe or Bay Street as alternatives.