Photo: The Canadian Press

The new Samuel de Champlain bridge is seen with the old bridge in the background in Montreal.

Montreal's expensive new Samuel De Champlain Bridge opened to traffic for the first time this morning, about six months behind schedule.

Federal Infrastructure Minister Francois-Philippe Champagne was riding in one of the first cars that rolled northbound across the newly built span at 5 a.m.

The 3.4-kilometre bridge over the St. Lawrence River counts three lanes in each direction, plus a central deck for public transit, as well as a multifunctional path for cyclists and pedestrians.

It was originally scheduled to open last December, but various delays pushed back the opening and added another $235 million to the original $4.2 billion price tag.

The bridge is open northbound only for the first week — the second phase of the inauguration is set to take place on July 1, when the lanes heading off the island will open.

The crumbling 57-year-old bridge it replaces, which has long been one Canada's busiest spans, will be dismantled over the next three or four years.