An MR-63 train at Honoré-Beaugrand station on the green line
Running through the heart of Montreal's central business district, the green line is a backbone for the network. The stations between Atwater and Berri-UQAM are the 6th, 4th, 7th, 1st, 9th, 49th, and 2nd busiest stations in the network. Trains on this sector can become extremely congested during rush hour; the largest part of the traffic is between downtown and Berri-UQAM, thence to the south shore by the yellow line and to the Plateau, Montreal-North, and Laval by the orange line. This line also serves the neighbourhoods of Verdun, the Sud-Ouest, the Centre-Sud, and Hochelaga-Maisonneuve.
Early plans called for the line under rue Saint-Denis to curve northward from the financial district through Dorchester Square westward with stations at Peel, Guy, and Atwater, with extensions foreseen west throuqh Westmount and NDG and forking east throuqh downtown, intersecting at Berri, and branching north and east. The origins of the green line as bullt can be seen in these plans.
Initial network construction
The first section of the line to be constructed was between Atwater and Frontenac. The line operated only as far as Papineau from the metro's inauguration on October 14, 1966, until December of that year, when Beaudry and Frontenac stations were also opened. This portion, built to serve the commercial artery of rue Sainte-Catherine, was built one block to the north, under Western, Saint-Luc, Burnside, Ontario, and de Montigny streets, so as not to disrupt traffic on Sainte-Catherine during construction. Most of this section was built in open-cut, and when the dig was covered over the different streets were unified into boul. de Maisonneuve.
The line was extended eastward as far as Honoré-Beaugrand in time for the 1976 Olympics (the Olympic installations are served by Pie-IX and Viau stations). This section was the first extension for the metro. It was built with the usual bowl-shaped interstation profile that allows the train to use gravity to help accelerate and brake, resulting in energy savings.
The westward extension to Angrignon followed, including Lionel-Groulx station that was built as a transfer station in preparation for the orange line that would meet it two years later. The bedrock in this area is of rather poor quality - much of it is Utica shale, softer and weaker than the rock in other areas of the island. As a result, two stations, Charlevoix and De L'Église, had to be built with one platform over the other to have as small a cross-section as possible, and all of the other stations except Monk had to be dug in trench. (Most of the metro's other extension stations were built in tunnel with one or two shafts built in trench for access.)
Early expansion plans called for the addition of light rail systems to serve areas beyond the line's terminuses. These plans were shelved and there are no current proposals to extend this line.