The sudden closure of the southbound Louis-Hippolyte-Lafontaine tunnel is already amounting to a traffic nightmare for Montreal commuters.

Transport Quebec announced a three-day closure of the tunnel in the direction of the South Shore Wednesday night after corrosion was found on beams supporting the paralumes – the light-dimming structures at the entrance and exit of the tunnel.

"We decided to close the tunnel because it was the safest thing to do and to make sure that the work would be performed as rapidly as possible," Transport Minister Pierre Moreau told CBC Montreal Thursday morning.

"Whenever there will be a doubt, I will not hesitate to close a section of the network that is not safe and exactly that’s what I did yesterday."

The south lanes of the tunnel will remain closed until at least Dec. 24 at 11 p.m. Traffic is being re-routed to the Jacques- Cartier Bridge.

Two out of the three lanes headed toward Montreal will also be closed from 9:30 p.m. to 5 a.m. on Thursday and Friday nights.

The paralumes have already proved treacherous in another of Montreal's tunnels. It was a support to one of the shades that collapsed in the Ville Marie tunnel in July.

The paralumes were removed from that roadway in November.

'Security is non-negotiable'

Montreal Mayor Gerald Tremblay said the prompt decision to close the Lafontaine tunnel was the right one.

"Security is non-negotiable," he said. "We lived through Ville Marie and we saw what could have happened."

Tremblay encouraged commuters to take public transit and carpool to avoid some of the anticipated traffic headaches.

The Montreal Transit Corporation has boosted service on its yellow line to and from the South Shore to accommodate commuters who leave their cars at home. It will continue until the tunnel reopens.

The city has asked the police service to help direct traffic going to the Jacques-Cartier and Victoria bridges, he said.

Traffic tie-ups were reported across the island Thursday morning as drivers tried to negotiate the newest restriction on Montreal arteries.

Marc Cadieux, head of the Quebec Trucking Association, said the sudden closure of the tunnel amounted to "chaos and a bit of frustration," Wednesday night.

'Our losses have been great for the last months so obviously there’s a domino effect and the cost of this has to be relayed to the consumer unfortunately.'—Marc Cadieux, Quebec Trucking Association

"We try to always do our best toward our members in trying to assess that kind of information, but obviously a lot of companies are already shut and the trucks are on the road," he said.

Earlier in December, Transport Quebec announced new restrictions on the Turcot Interchange that prohibits heavy trucks from accessing Highway 15 south toward the Champlain Bridge because of safety concerns.

The ongoing restrictions and detours have left some trucking companies forced to tack on surcharges for deliveries to the island during peak periods, Cadieux said.

"There’s fuel, there’s hours of services. . .  there’s a lot of logistics behind all this so it’s what we’ve been facing," he said.

"Our losses have been great for the last months so obviously there’s a domino effect and the cost of this has to be relayed to the consumer unfortunately."