Drivers heading south on I-405 will use a new freeway bridge over I-90 starting Tuesday morning.

Traffic will transition to the new 900-foot-long southbound bridge in phases. Initially the new bridge will carry two of three southbound I-405 lanes.

The carpool lane will remain on the existing southbound bridge. The phased opening and lane separation are necessary to create a safe work zone for more construction near the bridge.

“This bridge opening represents a major project delivery milestone,” said Paula Hammond, Secretary of Transportation. “The South Bellevue Widening Project directly addresses congestion relief, which is a key commitment in our Moving Washington strategic plan. I-405 carries over 800,000 people a day, many of those to and from growing employment areas, like Bellevue – it’s critical to our economy that we keep this traffic moving.”

According to WSDOT’s annual report on highway congestion published in November, the section of I-405 freeway from Tukwila to Bellevue remains the most congested commute in the state.

The new configuration will feel different to drivers, however.

“It will take time to get used to this temporary configuration”, said Seema Javeri, WSDOT Project Engineer, “so drivers traveling southbound on I-405 should prepare for minor delays for the first few days of their commute.”

Javeri expects after commuters drive over the bridge a few times, they’ll become familiar with it and drive accordingly. Until then drivers should proceed with caution, she added.

By next summer crews expect to wrap up bridge improvements and then shift the southbound carpool lane to the new bridge. That will free up the existing bridge to carry an additional northbound lane.

The work is part of the I-405, South Bellevue Widening project that adds one northbound lane between 112th Avenue SE and SE Eighth Street and two southbound lanes from SE Eighth to I-90. To date, WSDOT has delivered 30 percent of the nearly $1.5 billion in I-405 investments and is on track to reach 44 percent by then end of the 07-09 biennium.

For more information and a diagram of the new traffic configuration visit the project web site at www.wsdot.wa.gov/Projects/i405/.