Heading west from Montreal's downtown core is now drastically different as two entrances to Highway 720 and two entrances for Highway 20 have been eliminated.

Drivers can access the westbound highway from Viger Ave. or from a new entrance on Rose de Lima, but nowhere in between.

Transport Quebec expects the worst traffic will be every afternoon as drivers from the downtown core line up along St. Antoine St. to enter the westbound highway, although a police officer will be stationed at the intersection in an attempt to ease delays.

“If you're able to change the time of commute that would be the best option,” said Sarah Bensadoun, a spokesperson for Transport Quebec.

The Fort and Lucien L'Allier entrances to the westbound Ville Marie have been closed and will remain closed until 2019 because the elevated portion of the highway is being demolished.

Instead, drivers come out of the tunnel and swerve left to the lowered section of the new Route 136.

Meanwhile, the westbound lanes of Highway 20 have shifted north, closer to the escarpment, and the exit for Angrignon Blvd. is on the right-hand side.

There is also going to be a new entrance for those who head west from Ste. Anne de Bellevue Rd. and Angrignon Blvd. Those motorists will get onto Pullman Rd., then enter Highway 20 West from the left-hand side.

Important note: the speed limit on many ramps is reduced to 50 kilometres per hour.

The decades-old entrances at Monk St. and Notre Dame St. for Highway 20 West no longer exist because the westbound lanes for Highway 20 have shifted north -- on the other side of the eastbound lanes.

The new configuration also affects drivers coming from Highway 15 north and south who want to head west, which led to some drivers not knowing what to do.

"There was some confusion this morning especially for those who are on Decarie. They wanted to access the 20 west but they forgot to keep to their left because that is one of the new changes we put in place this weekend," said Bensadoun.

Those coming from the Decarie Expressway who want to head west will have to be in the centre lane -- which will curve to the east, as if heading downtown, before looping around and going underneath the highway.

Those who ignored the signs wound up near the Champlain Bridge.