The Western section includes a four-lane divided highway that begins at Autoroute 20 in Vaudreuil-Dorion, including the redesign of Autoroutes 20, 30, and 540. The highway is 35 km long, and connects with Route 138 (boulevard René-Lévesque) at the boundary of Châteauguay and Mercier. This section of the project also includes work on the following highways.
The completion of Autoroute 30 will involve the construction of several structures, specifically intended to maintain the existing road links and involving the redesign of certain interchanges.
The Western section also includes two major structures that will make it possible to cross two large waterways:
The total investment in these bridges represents more than 40% of the cost of the Western section, and must satisfy certain criteria that have been previously negotiated with the federal government and with the St. Lawrence Seaway Management Corporation.