The southern section of A-15 connects the south shore suburbs of Montreal and is also the primary trade corridor route between Montreal and New York City linking Quebec Autoroute 15 to Interstate 87 at the Canada-United States border at the Champlain-St.
Bernard de Lacolle Border Crossing.
This was the former Route 9, and connected with US 9 on the western shore of Lake Champlain.
In Brossard, it joins up with A-10 and A-20 across the Champlain Bridge into Montreal.
The A-10 splits off almost immediately after crossing the bridge to head into downtown Montreal at the Bonaventure Expressway and the A-20 splits off shortly after at the Turcot Interchange (échangeur Turcot), leaving the A-15 to continue northward as Autoroute Décarie until the Décarie Interchange (échangeur Décarie) with the A-40 at the point where it turns from the Trans-Canada into the Metropolitan Expressway.

The route is also connected to Autoroute 30 in Candiac which was completed to Autoroute 20 in 2012 providing a quicker access to the south shore of Montreal, to southern communities located alongside Autoroute 15 and to the Canada–US border in Lacolle.
It will also give a quicker access from there to areas west of Montreal and also Ottawa and Gatineau.
The southern section of A-15 connects the south shore suburbs of Montreal and is also the primary trade corridor route between Montreal and New York City linking Quebec Autoroute 15 to Interstate 87 at the Canada-United States border at the Champlain-St. Bernard de Lacolle Border Crossing. This was the former Route 9, and connected with US 9 on the western shore of Lake Champlain. In Brossard, it joins up with A-10 and A-20 across the Champlain Bridge into Montreal. The A-10 splits off almost immediately after crossing the bridge to head into downtown Montreal at the Bonaventure Expressway and the A-20 splits off shortly after at the Turcot Interchange (échangeur Turcot), leaving the A-15 to continue northward as Autoroute Décarie until the Décarie Interchange (échangeur Décarie) with the A-40 at the point where it turns from the Trans-Canada into the Metropolitan Expressway.
The route is also connected to Autoroute 30 in Candiac which was completed to Autoroute 20 in 2012 providing a quicker access to the south shore of Montreal, to southern communities located alongside Autoroute 15 and to the Canada–US border in Lacolle. It will also give a quicker access from there to areas west of Montreal and also Ottawa and Gatineau.
Quebec Autoroute 15