SR 520 Bridge Replacement and HOV Program - Practical design

The SR 520 construction program is applying WSDOT's Practical Solutions strategy to produce more flexible and sustainable transportation investments. "Practical design" is part of this strategy. 

Practical design is an approach to making project decisions that focuses on the need for the project and looks for cost-effective solutions for meeting those needs. Practical design engages local stakeholders at the earliest stages of defining projecdt scope to ensure that public input is included at the right stage of project design.

Meeting diverse interests

Major highway projects in a large urban area must address a diverse mix of public interests and demands. Transit supporters want greater bus, rail and carpool options. Businesses need reliable delivery of goods and services. Urban neighborhoods desire a smaller project footprint. Commuters want less congestion. Foot-powered advocates seek more and safer bicycle and pedestrian routes. Taxpapers want accountable spending.

With practical design, the result is smarter, more effective designs that achieve maximum results with limited funding, and that better suit the project's needs without compromising safety or community involvement. Below are examples of ways in which the SR 520 program has reduced costs or improved results.

Narrower lanes and shoulders 
Practical design helped us identify an opportunity to narrow highway shoulders, in some places by as much as eight feet, on the new floating bridge, West Approach Bridge North and the planned Portage Bay Bridge. While ensuring safety and mobility, the strategy saves the projects millions of dollars in construction costs by reducing concrete, steel and other needed bridge materials. It also reduces the environmental footprint of the bridges, a context-sensitive solution found in response to community input.
Smart highway technology 
The new floating bridge and improved corridor use smarter highway technology like variable speed-limit signs and reader boards displaying real-time traffic information. This technology, often referred to as active traffic management (ATM), increases roadway efficiency and helps drivers travel safer and smarter.

Fewer bridge columns
In consultation with the Seattle Design Commission, WSDOT reduced the number of permanent, in-water columns supporting the West Approach Bridge North. This design change cut by 40 percent the amount of concrete needed for the project, saving money and reducing the project's environmental impact while supporting WSDOT's sustainability goals.

A smarter Montlake lid

We redesigned the future, multimodal Montake freeway lid to work better for its users. We eliminated costly ventilation and maintenance systems, which reduces costs for construction materials and long-term maintenance. Our design change also retained the lid's desired public space, removed unusable space, and improved transit, bicycle and pedestrian accessibility.  

Lowered speed on the Portage Bay Bridge
The new Portage Bay Bridge will have a speed limit of 45 mph. This reduces the noise caused by tires on the pavement, reducing the bridge's impact on the surrounding neighborhoods.