The Décarie Autoroute is a sunken highway between the northbound and southbound lanes of Decarie Boulevard from the Metropolitan Autoroute at its northern end to Monkland Avenue and the Villa Maria Metro station at its southern end.
It was built on a wide expanse of vacant land, donated to the city by the Décarie estate on the condition that a streetcar line would be established.
The decommissioning of the streetcar system in 1959 left the right-of-way as an obvious choice for a highway and so the Décarie Autoroute was dug there.
South of Queen Mary Road, however, were a significant number of houses that were demolished.

To avoid demolishing Notre-Dame-de-Grâce Church, the highway makes a slight westerly jog below Côte-Saint-Luc Road and runs through a short tunnel, before emerging between Addington and Botrel Streets and running down to Sherbrooke Street and Saint Jacques Street, where it spectacularly goes from being below the ground to well above the ground as it intersects with Autoroutes 20 and 720 in the infamous Turcot Interchange (dubbed "Spaghetti Junction" by train crews operating the former CN Rail Turcot Yard).
Following the conversion from streetcar line to highway, the Décarie estate sued the city but was unable to prevail because its did not document its case well enough for the nevertheless-sympathetic court.
The Décarie Autoroute is a sunken highway between the northbound and southbound lanes of Decarie Boulevard from the Metropolitan Autoroute at its northern end to Monkland Avenue and the Villa Maria Metro station at its southern end. It was built on a wide expanse of vacant land, donated to the city by the Décarie estate on the condition that a streetcar line would be established. The decommissioning of the streetcar system in 1959 left the right-of-way as an obvious choice for a highway and so the Décarie Autoroute was dug there. South of Queen Mary Road, however, were a significant number of houses that were demolished.
To avoid demolishing Notre-Dame-de-Grâce Church, the highway makes a slight westerly jog below Côte-Saint-Luc Road and runs through a short tunnel, before emerging between Addington and Botrel Streets and running down to Sherbrooke Street and Saint Jacques Street, where it spectacularly goes from being below the ground to well above the ground as it intersects with Autoroutes 20 and 720 in the infamous Turcot Interchange (dubbed "Spaghetti Junction" by train crews operating the former CN Rail Turcot Yard). Following the conversion from streetcar line to highway, the Décarie estate sued the city but was unable to prevail because its did not document its case well enough for the nevertheless-sympathetic court.
Quebec Autoroute 15