The Turcot Interchange is the busiest highway structure in Montreal, and is showing its age. (Canadian Press)The Quebec government has unveiled its $3-billion plan for rebuilding the Turcot Interchange in Montreal amid grumbling from some local politicians.

The province's transport ministry was forced to go back to the drawing board after its earlier plan was criticized — and calls its new blueprint a greener and more public-transit friendly solution.

It's also more expensive. The estimated price tag revealed is double what earlier figures predicted.

Montreal Mayor Gérald Tremblay is backing the proposal after sparring with the province about public transit concerns around the critical highway interchange.

"It sets aside a major place for public transit," Tremblay said at a news conference Tuesday. "It will help minimize expropriations."

But opposition parties dismissed the plan, calling it manipulative and unrealistic.

New Turcot to be built north of current site

A video presentation by Quebec's transport ministry promises a "harmonious urban integration" of the new expressway and interchange, with images of cyclists, tramways and lush green spaces surrounding the future highway structure.

The new highway will be north of the current one, with a reserved lane in each direction for buses, taxis and carpool vehicles. Tremblay said it would "encourage the creation of a vast new neighbourhood" between Highway 20 and the Lachine Canal.

There are several large factories in that space right now, and Transport Quebec's plan doesn't include measures to purchase, expropriate or move any of them.

That leaves a modest space for any new neighbourhood, about three kilometres long and 150 metres wide, Projet Montréal Leader Richard Bergeron said.

Only a "pseudo-neighbourhood" could sprout in such a space, said Bergeron, a former urban planner with the City of Montreal.

"Can you imagine a neighbourhood with a highway on one side, and big industry on the other? It's impossible!"

Bergeron accused the province of manipulating the public into believing the plan is sustainable. "They lied this morning," he said simply.

Vision Montréal Leader Louise Harel echoed Bergeron's concerns, saying the new design will isolate Montreal's southwest borough. "Barriers divide the population, and it's worse for people who live there," said city hall's opposition leader. "What they proposed is a virtual world, but it doesn't exist in reality."

An elevated bike path and pedestrian walkway will link the area around the Lachine Canal to a new green space between the highway and Saint-Jacques Street West.

The government originally expected to expropriate 20 buildings in the area, however that number has been reduced to four. More than 100 families, including many artists, will be eventually displaced.

Government officials estimate that 290,000 vehicles will travel through the interchange on a daily basis when it is complete.

The new roads and ramps will be built around the existing structure to minimize road closures and traffic headaches during the lengthy construction period.

The new interchange is slated to be complete by 2017-2018.

Transport Quebec will build the new Turcot Interchange around the old one to minimize the impact during the construction phase. (Transport Quebec)