That’s according to a federally-commissioned study obtained by Radio-Canada.
The study was conducted for Transport Canada by the British firm Steer Davies Gleave.
Denis Lebel commissioned the study while he was the federal minister of transport, asking the British firm to look into the effect tolls would have on traffic and revenue.
The Quebec government and the Coderre administration have been demanding to see its results, but Transport Canada refused to release its findings.
In the copy obtained by Radio-Canada, the study suggests that 30,000 vehicles a day would migrate to other bridges if a $2.50 toll was charged during rush hour.
Most drivers would go to the Victoria and Jacques Cartier bridges.
That would increase traffic on the Victoria Bridge by more than a third — reaching 135 per cent of the span’s maximum capacity during rush hour.
Traffic on the Jacques Cartier would go up 15 percent — to 175 per cent of its capacity at rush hour.
“The analysis of historical data shows that the other spans would already exceed, in some cases, a traffic volume of more than 100 per cent,” the study says.
If Ottawa were to charge more than $2.50, it would have an even greater effect on traffic.
For instance, if the toll were $4.40 per car, and more for trucks, the volume of rush-hour traffic would double on other bridges, while the Champlain Bridge would have very light circulation.
“The tolls would reduce traffic on the new bridge and this raises concerns because the diverted traffic cannot be absorbed elsewhere in the network," the study says.
A credible poll?
According to an opinion poll in the study, 56 per cent of people agree with tolls, while 32 per cent are against.
Some experts question the poll’s sample size, as well as its findings.
In all, 2007 people were paid to participate in the internet poll.
Of that number, the vast majority said they travel between Montreal and the South Shore less than three times a month.
Also, about 75 per cent of respondents said they crossed the bridge to go shopping or for recreational activities, while only 25 per cent said they used the bridge to get to work or school.
And of all those polled, only two people said they crossed the bridge between 10 and 14 times a week.
The authors of the study, Steer Davies Gleave, have offices in London, Boston and Vancouver, and sources say have only limited knowledge of the greater Montreal area.
Transport Canada did not respond to CBC’s request for an interview.
Study never made public
The federal government never released the firm's findings.
In an email to Radio-Canada, Infrastructure Canada said that the publication of the study could “influence the proposals of bidders in the procurement process that is underway, which could result in Canadian government not getting the best value for Canadians.”
Infrastructure Canada added that "further studies and consultations will take place before the toll for the new bridge can be established."