Expect regular traffic jams downtown, especially during the weekends for roughly the next two years.

That was the take-home message from traffic planners who met reporters Wednesday to brief them again about upcoming road closures in the Turcot Interchange, used by 300,000 motorists daily. And they were more clear about an end date for the work to demolish and rebuild the expressway: midto late 2019, meaning nearly two years of traffic chaos slated for the downtown core.

Starting Monday, the westbound Ville-Marie Expressway will be completely closed, including the entrances from Fort and Lucien L’Allier Sts. Westbound traffic will be diverted to the eastbound side, and the only two access points to those lanes will be on Hotel-deVille Ave. near city hall (which can be accessed from both St-Antoine St. and Viger Ave.), and a temporary access at Rose-de-Lima St. at the corner of St-Antoine.

The closures will probably affect anyone driving in Montreal either directly or indirectly, as gridlock is expected to spread to alternate highways and local streets. Traffic planners expect Atwater Ave., René-Lévesque Blvd. and St-Antoine St. will be among the streets affected.

For Notre-Dame-de-Grâce and Westmount residents, the St-Jacques St. exit off the VilleMarie near the MUHC superhospital will be closed. Accessing the Champlain Bridge from the VilleMarie will be impossible, as the Highway 15 South entrance will also be closed.

At least one local traffic observer was alarmed about the planned closures.

“My suspicion is that a lot people will use René-Lévesque and some of the lateral routes that can’t really handle (that traffic),” said Rick Leckner, a former radio traffic reporter. “So, really, what has to be ensured is that there is very strict monitoring all the time.”

The news is particularly bad for anyone who drives in and out of downtown on weekends, as the Ville-Marie in both directions will be closed virtually every weekend this fall and winter while the existing roadway is demolished. But it gets worse.

On some weekends, the closures will extend on Highway 20 all the way to 1st Ave. in Lachine, and Highway 20 West will be inaccessible from Highway 15 North.

Transport Quebec spokesperson Sarah Bensadoun said because of the complicated nature of the work, the Transport department can’t give an advanced schedule of the weekend closures.

“Since we have a lot of work that is conducted during the weekends, the different teams reevaluate the progress on Monday and Tuesday, so that is why we can only advertise different closures three to four days in advance,” Bensadoun said.

Weekend road closures are going to be the norm, rather than the exception until the old VilleMarie structure is demolished and rebuilt, planners warned.

Here are more details of how the roadwork will affect motorists until the middle to end of 2019:

Already a scene of major gridlock, especially in the morning, the south end of the Décarie is about to get worse for anyone using it to get east or west.

Drivers heading to Highway 20 West or downtown on the VilleMarie East will have to use the left two lanes at the south end of Décarie. Those heading west will have to stay in the left lane to first go east to St-Rémi St., and then double back on some temporary roads to get to the new Pullman Blvd. Once there, they will be merging with all the traffic detoured off Highway 15 North, because that highway’s exit for Highway 20 West will also be closed. Motorists heading to the Ville-Marie will have to stay in the middle lane to get there.

Motorists heading to the Champlain Bridge or Verdun from Décarie will find no change in how they access Highway 15 South.

The de la Vérendrye Blvd. entrance to southbound Highway 15 will be closed until the project’s completion in 2020. The access to Highway 20 West will remain closed and the detour route, put in place in September, will remain.

There is some good news for those driving in the westernmost part of the project.

It will be easier to exit at Angrignon Blvd. from Highway 20 West. The exit will be on the right-hand side, which Transport Quebec acknowledged is “more natural” than the old configuration that had motorists driving in the left lane to get to the exit.

The Angrignon Blvd. entrance to Highway 20 East will also be reworked, and the Highway 20 West entrance at that spot will be relocated to its permanent spot at the end of Ste-Anne-de-Bellevue Blvd. The Notre-Dame St. entrance to Highway 20 West in that sector will be closed.

Highway 20 will have cars driving on the right side throughout the Turcot Yards starting Monday. Currently, the lanes criss-cross twice so motorists are driving on the left-hand side for about one kilometre.

Traffic planners advise motorists to stay abreast of the closures by consulting the project’s website or using Waze or Google Maps, which will be updated with the road closures.

When this phase of work is done in 2019, there should be four lanes in each direction on the Ville-Marie again. When the project is fully completed in 2020, traffic capacity in the interchange will remain as it was before the project began.