Oh yes Marc Dufour's website, I found a lot of interesting information about the Montréal Métro while I was writing a research paper about it. While Paris was the first city to use this technology, Montréal was the first to initially adopt it on the entire subway network.
This technology permitted having steeper grades and sharper curves for the Montréal Métro. Most tunnels between the stations "dips", which permits the trains to accelerate by aid of gravity, and same thing by slowing down while entering a station.
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Here is a photo I took of a tunnel going down leaving the station.
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