Toronto, Canada's most populous city, currently has three metro lines in operation. Around 2.7 million people live in the city of Toronto alone, and as many as 6.7 million in the Greater Toronto Area. The Eglinton Line as a fourth line will add another east-west connection. Metrolinx planned use mechanized tunnelling to drive two parallel tunnel tubes, each 6.3 kilometers long, for the 9.2-kilometer-long “Eglinton Crosstown West Extension” section between the future stations of Mount Dennis and Renforth Drive.

The two Herrenknecht EPB Shields with a diameter of 6,550 millimeters, christened Rexy and Renny, started in an east-west direction in April and July 2022. After driving up to almost 240 meters per week under inner-city build-up areas, the tunnellers successfully reached the Scarlett Road target shaft with the two machines in April and May 2024.