Toronto's oldest and busiest transit route, the Yonge Street stretch of the Line 1 subway opened in 1954 terminating at Eglinton, extended north to Finch 20 years later. Since 1974, that has been the Yonge subway's northernmost point, but after years of planning, the U-shaped line's eastern branch is about to get its first extension in 48 years.

The Yonge North Subway Extension will add another eight kilometres of track and four stations to the line with a targeted in-service date of 2029-2030. The extension's opening may be some time away, but preparations are already being made for the first construction activity set to commence next year.

We may have to wait until 2023 to see major construction, but behind the scenes, boxes are being checked off in the complex process of constructing the extension that will bring Yonge subway service into neighbouring Vaughan, Markham and Richmond Hill.

Last year was a busy one for Metrolinx, 2021 seeing the reveal of updated plans for the project and confirming that the new terminus will be known as Clark Station. But the biggest news out of last year was the start of a search for teams to upgrade the existing terminus at Finch Station to prepare for its integration into the extension.

With the 2023 start of these so-called 'early works' and the accompanying disruption at street level fast approaching, a winning bid to undertake this element of the project will be selected this year.

We should learn more details about tunnel boring machines for the extension this year, with Metrolinx gearing up to issue a 'Request for Qualifications' or RFQ for the line's tunnels, which will open up the bidding process.

Other background activity getting the wheels moving for this project includes work on updated environmental studies that assess the impacts of construction and operation of the new line. The latest work on these studies factors in recent changes to the route's north end, revised last year to appease local concerns.

Building on previous environmental studies conducted in 2009 and 2014, this Environmental Project Report is expected to be released in the coming weeks, followed by opportunities for public engagement, which will inform the study's final report later this year.