I-405 Widening and Express Toll Lanes Design-Build


Transpo Group is part of the Flatiron Construction Design-Build team for WSDOT’s I-405 NE 6th Street to I-5 Widening and Express Toll Lanes project. The project creates one continuous northbound and southbound lane between NE 6th Street in Bellevue and SR 522 in Bothell. The project is converting the existing carpool lane into a dual express toll lane system from downtown Bellevue to Bothell, and includes safety and capacity improvements to the general lanes. Transpo’s services include traffic engineering, ITS (intelligent transportation systems), signage, pavement marking, traffic signals, and maintenance of traffic.

Transpo is completing the comprehensive signing plan for the corridor , including both general purpose lanes and dynamic toll system signage. This includes preparing a full inventory of existing signage, designing signage related to work zones and detours during construction, and detailing final signage plans. The final signage plans are based on federal and state standards, and include signage related to tolling in the corridor , which change based on time-of-day and traffic volumes. These signs are setting the precedent for future tolled facilities in the region, and are the first of their kind to be installed in Washington.

Transpo is also designing the infrastructure for the tolling system and all WSDOT ITS equipment along the corridor including conduit, fiber, power, and associated cabinets and boxes. On intersecting local streets, Transpo is upgrading four signalized ramp terminals and designing one temporary traffic signal, providing updated accessible pedestrian crossings, improved vehicular detection, and fiber interconnection with WSDOT ITS.

The new express toll lane system will provide 17 miles of additional congestion relief to Bellevue, Kirkland, and Bothell. Learn more about the 405 Express Toll Lanes on WSDOT’s project website.