Montreal’s new $4.4-billion Samuel de Champlain Bridge officially opened to traffic in one direction on Monday morning.

The 3.4-kilometre span over the St. Lawrence River took four years to complete and is expected to last 125 years.

The former Champlain Bridge, which will be demolished over the next four years, was constructed in 1962 but deteriorated quickly due to the corroding effect of road salt on its steel parts.

It’s considered one of the most important links in Canada, with about 50 million vehicles crossing it annually and roughly $20 billion of Canada-U.S. trade passing over it each year.

Suzanne Beinvenu of Nuns’ Island, which links the bridge with Montreal and the south shore community of Brossard, was among the first to cross at 4 a.m.

“I put my alarm on and convinced my neighbour to come so he was my driver and I could look at the bridge and the city,” she told CTV News Montreal. “It’s just amazing.”

Minister of Infrastructure and Communities Francois-Philippe Champagne was also on hand for the early morning unveiling.

“Every centimetre I was crossing, I was thinking about the 2,000 men and women who have delivered signature infrastructure for Montrealers,” he said.

Gregorio Munoz, a worker with the Signature on the Saint Lawrence consortium that constructed the bridge, said the project was “non-stop work since 2015.”

“I don’t have words to describe the feeling we have,” Munoz said while grinning.

Only the northbound lanes opened Monday. The southbound lanes are expected to open on Canada Day. The bridge will eventually have a light rail track, pedestrian walkway and bike lanes.

The new bridge was originally announced in 2011. The federal government promised it would be completed by December 2018, and set fines for delays of $100,000 per day for the first seven days, and $400,000 per day after that, up to $150 million.

Minister Champagne said there will be consequences for the delays. “The contract is very clear what needs to happen,” he said.