Route 342 is a provincial highway located in the Montérégie region of Quebec west of Montreal. It runs from the Ontario-Quebec border in Pointe-Fortune (at the junctions of Ontario Highway 417 and Autoroute 40 and ends in Vaudreuil-Dorion at the junction of Autoroute 20. Its main purpose serves a service/alternate route to Autoroute 40 and has 4 interchanges with it in Pointe-Fortune, Rigaud and Hudson.