A new pedestrian tunnel will soon link a pair of Toronto transit stations after years of planning and delays.

Metrolinx is building a new 270-metre-long pedestrian connection linking Bloor GO/UP Express Station and the TTC's Dundas West Station — turning the two disconnected stations into a new multimodal interchange.

It sounds simple enough, but it's actually a complex undertaking that involves drilling and digging the new passage, all without disrupting access to Bloor GO Station or train service along the corridor.

This is possible, in part, thanks to an alignment that runs below the parking area of The Crossways, a residential and retail complex that stands between the two stations.

Construction is underway on a 270-metre underground pedestrian tunnel extension. As part of GO Expansion, the tunnel will allow customers to enjoy a safe and accessible connection between Bloor GO/UP Station and the Dundas West TTC Station. pic.twitter.com/7D58erD3Iq

— GO Expansion (@GOExpansion) July 4, 2024

The video above shows how work at the east end of the tunnel site is being carried out adjacent to, but not restricting rail activities on this shared GO and UP Express corridor.

Construction on this so-called "missing link" began earlier this year, but it took decades of planning and negotiation to get to the ongoing construction progress visible today.

The project was first tabled and approved during Bob Rae's NDP provincial government in the mid-1990s.

Toronto to get 'missing link' pedestrian tunnel connecting two transit stations https://t.co/7BMlSBHiAe #Toronto

— blogTO (@blogTO) August 31, 2023

However, the plan would stagnate for decades until Ontario's Ministry of Transportation announced that it would finally move forward in 2023.

Once complete, passengers will be able to transfer between the GO Transit/UP Express routes and the TTC's Line 2 subway without having to brave the elements or dodge traffic at street level.