Drivers are being warned to avoid the Port Mann Bridge area if they can this weekend as construction crews replace the Cape Horn interchange.

Highway 1 westbound will be reduced to just one lane at the Cape Horn from Saturday night to Sunday afternoon. Also, access to Highway 1 eastbound from the Lougheed Highway westbound will be closed.

Drivers will have to use Brunette Avenue instead.

The Coquitlam interchange, built in the 1960s, is the busiest in the province, carrying 120,000 vehicles a day — and an update is long overdue.

"The current configuration has all of that traffic sharing a very small and limited capacity overpass,” said project spokesman Max Logan.

The interchange provides access to Highway 1, the Port Mann Bridge, the Mary Hill Bypass, United Boulevard and Lougheed Highway, with traffic connecting to the northeast sector of Metro Vancouver as well as downtown Vancouver and other communities west of the bridge.

4 interchanges become 15

The improvements “will address congestion on Highway 1 by improving traffic flow between major arterial roads, and improve safety by reducing traffic weaving and designing ramps to accommodate commercial vehicles,” according to the Port Mann/Highway 1 Improvement Project website.

With the new design, the number of interchange structures — overpasses and underpasses — will increase from four to 15 to assist in providing direct connections between Highway 1 and major arterial roads.

Logan says each of the new structures will carry a separate stream of traffic, resulting in safer roads.

Despite the dramatic differences, Logan believes some things won’t change.

"Well, I think it’s forever going to be known as the Cape Horn interchange."

The new road system is scheduled to open on Monday.

But there will be more disruption next weekend. From Friday evening to Sunday morning, Highway 1 will be reduced to one lane in each direction so the old Cape Horn Interchange can be torn down

With files from the CBC's Kirk Williams