Metrolinx - Tunnelling
Building tunnels in large and busy urban areas is a complex job. It’s one of the topics we’re asked about the most as we add dozens of kilometres of new underground transit to the regional transportation network. The tunnels that carry underground transit routes are built to accommodate the trains that will travel through them, a flat concrete surface at the bottom for the tracks, a safety walkway that can also be used for maintenance access and emergency evacuations, and systems for power, sign