Ever wondered how the subway tunnels you ride every day were built? The answer lies in Tunnel Boring Machines (TBMs), some of the largest and most complex machines used in modern infrastructure construction. These massive machines carve tunnels deep underground. However, transporting them to the job site is a major heavy haul project on its own.
After arriving in Ontario from Germany, TBMs Libby and Corkie still had a long journey ahead before reaching their final destination. Scott-Woods had the honour of supporting their transportation journey every step of the way.
The Scale of Tunnel Boring Machines
The cutting head of the TBM alone is massive, measuring nearly 23 feet in diameter and weighing approximately 167,551 pounds. In total, transporting the cutting head and additional TBM components required roughly 44 specialized truckloads!
Once fully assembled, a TBM can reach 300–330 feet in length and weigh close to 900-1000 tonnes. These enormous dimensions highlight the scale and complexity of the machines used to build major transit infrastructure projects.
Once fully assembled, a Tunnel Boring Machine can reach 300–330 feet in length and weigh close to 900–1000 tonnes (roughly 2.2 million pounds), highlighting the scale and complexity of these transportation projects.
Photo Credits – HOPA Ports
Moving Through Toronto
Recently, in February 2026, the components were carefully moved from the Uxbridge yard through Toronto to the Exhibition Line site, in partnership with Mammoet, for the last leg of their journey.
Moving equipment of this size through a busy city comes with significant challenges. Coordinating permits and navigating tight city streets required detailed planning, especially considering some components were nearly two lanes wide.
Libby and Corkie will excavate the first two tunnels for the Ontario Line. Working side by side, the Tunnel Boring Machines will dig roughly six kilometres of twin tunnels beneath Toronto’s downtown core, helping build the next generation of transit infrastructure for the city. The names pay tribute to two communities along the route: Liberty Village and Corktown.
With one TBM now fully delivered, the job isn’t over yet. Another machine still needs to make its way into Toronto, so keep an eye out — you may spot another Scott-Woods heavy haul convoy moving through the city soon.