Line 6 was a proposed surface-running line of the Montreal Metro. Unlike the rubber-tire technology used on the Metro's current lines, Line 6's trains would have run on steel wheels. Planned as the first of a series of new routes along existing railways, in 1982 the Ministère de Transport du Québec expected Line 6 to begin service along 23.3 km of Canadian National railway tracks by 1989. Intersecting the Orange Line (Line 2) at Du College and Sauve stations (along with a planned transfer with the also-unbuilt Red Line, or Line 3), the line would have had 11 stations. Running along the northern part of the island, it would have passed through the then-independent city of St. Laurent, Ahuntsic, Saint-Michel, Montreal-Nord, Riviere-des-Prairies and Pointe-aux-Trembles. Planned stations included elevated stops along viaducts, and ones at ground level.
According to the MTQ, trains would have run every five minutes during rush hour and every fifteen minutes the rest of the day, at a speed approximately twice that of the underground Metro lines. Trains would have run in four-car sets during rush hour, and two cars the rest of the day.
Unlike the unbuilt Lines 3 (Red) and 7 (White), Line 6 never advanced far enough in the planning process to receive a colour.