I-405 - Renton to Bellevue Widening and Express Toll Lanes - Downtown Bellevue - Environmental Assessment - Key findings

Traffic improvements across all lanes for most trips 

Today, I-405 experiences traffic congestion many hours of the day in all lanes. Overall, the I-405 Renton to Bellevue Widening and Express Toll Lanes construction contract is expected to improve traffic across all lanes in most areas.

In 2025 at project opening, most trips during the morning and afternoon commutes in the downtown Bellevue area will be the same or better than if WSDOT did not build this project. However, northbound morning peak trips in the general purpose lanes would increase by about one minute.

Traffic levels are expected to increase over time. Still, with this project, travel times in 2045 would improve greatly during the southbound afternoon commute in the downtown Bellevue area. The trip between SR 520 and I-90 would take less than three minutes on average for drivers in all lanes. Without this project, the same trip would take nearly 19 minutes in the general purpose lanes and and 11 minutes in the HOV lanes.

However, for the northbound afternoon commute, 2045 travel times in the general purpose lanes would increase by about nine minutes with the project. That is because, if the project is built, southbound I-405 operations improve, allowing more vehicles to enter I-405 from I-90 and SR 520, increasing congestion north of the project area and in turn affecting the greater Bellevue area. Other unfunded Master Plan improvements are expected to provide future benefits that will improve travel times.


Tolling and socioeconomic considerations 

The addition of express toll lanes would improve I-405 speed and reliability for drivers who choose to use them. These benefits are especially important for carpools and transit, including riders of Sound Transit’s new I-405 Bus Rapid Transit line from Lynnwood to Tukwila, scheduled to open in 2024.

When combined with existing and future improvements, this project would create a continuous 40-mile express toll lane system on I-405 and SR 167 between I-5 in Lynnwood and the Pierce County Line. Express toll lane rules for this segment would need to be set by the Washington State Transportation Commission but are assumed to be similar to the Bellevue to Lynnwood operations.

WSDOT and FHWA examined the effects of the cost of the tolls and all-electronic toll system on low income and minority persons, and persons with limited English proficiency, known collectively as environmental justice populations. Any toll that charges all users the same amount, regardless of income, disproportionately affects low-income users. These effects would be offset by improved peak travel times in most locations, reliability and travel conditions in both the general purpose lanes and the express toll lanes. The project would not change the number of general purpose lanes or reduce general purpose capacity.


Environmental enhancements

  • Stormwater and water quality: The project adds new stormwater treatment for new and existing lanes. WSDOT will upgrade stormwater facilities to treat the increased highway runoff. The project will reduce pollutants and improve water quality for local wetlands and streams.
  • Ecosystems: The project is being designed to limit effects on local ecosystems as much as possible. The project would result in permanent loss of less than half an acre of wetlands and about two acres of vegetation adjacent to the existing roadway. These effects may reduce habitat available to local species; however, because the project area is highly urbanized, WSDOT does not expect any fragmentation or loss of connectivity of habitat. The analysis also concludes that there would be no adverse effects on Pacific salmon habitat. WSDOT will provide on-site and off-site mitigation for wetlands affected by the project.


Community effects

  • Air quality: WSDOT’s analysis shows that with improved vehicle technology and reduced idling, we expect improvements in overall air quality and reductions in greenhouse gas emissions as compared to existing conditions. Project construction would temporarily affect air quality because of increased equipment emissions and activities.
  • Noise: Aside from temporary construction noise, overall highway noise levels are expected to stay the same as today’s conditions.
  • Effects on adjacent properties: No businesses or residences will be displaced as part of this project. The new express toll lanes north of I-90 to Main Street will be created through a combination of converting the existing HOV lanes to express toll lanes and widening the existing freeway to accommodate the new lane. Widening would occur for the most part within existing WSDOT property. Minimal right-of-way is required, affecting five commercial and public properties.
  • Local connections and trails: The Project would improve connections for bicyclists and pedestrians through building portions of the Eastside Rail Corridor Regional Trail in partnership with King County.
  • Other resources not affected by the project: The project would have few effects on geology and soils; visual quality; hazardous materials; energy and greenhouse gases; historic, cultural, and archaeological resources; parks and recreation lands; and public services and utilties.

View and download the full Environmental Assessment and Discipline Reports