When it is completed the new Port Mann Bridge will be one of the largest of its kind in the world. (CBC)

Construction on the Highway 1 improvement project in Coquitlam, B.C, is moving ahead of schedule and the westbound traffic on the Cape Horn interchange is now moving at full capacity, officials say.

Traffic on the busy section of highway was reduced to one lane westbound overnight to allow crews to complete the final span of a new overpass.

But officials note work on the new interchange will continue and warn traffic along the Trans Canada Highway east of Vancouver will be reduced to one lane in each direction for most of next weekend, Sept 28. to Oct. 1.

The highway improvements are part of a major upgrade of the routes feeding onto the new 11-lane Port Mann Bridge that crosses the Fraser River between Coquitlam and Surrey, B.C.

Construction of the bridge is expected to be completed in December.