SR 9 - SR 531 / 172nd St NE - Intersection Improvements

Overview
We constructed a roundabout at the SR 9/SR 531 intersection to improve safety and relieve congestion.

Why is WSDOT going to improve the SR 9/ SR 531 intersection?
There is a significant amount of development planned in the near future for the land surrounding the SR 9/ SR 531 intersection. New developments will bring more homes, businesses and drivers. The current intersection isn't designed to handle the amount of expected growth. It won't be long before the increased development causes congestion, delays and collisions. We want to make improvements to the intersection before it fails.

On average 17,000 drivers use the SR 9/ SR 531 intersection on a daily basis. From 2004 to 2008 there were 28 collisions that resulted in 29 injuries. The majority of those collisions and injuries happened when drivers tried to turn left through the intersection. 

New residential growth is occurring to the east and north of the corridor. By 2025, the population is expected to increase by 75 percent in Arlington, and 64 percent in Marysville. The corridor is affected by this population growth, especially during peak travel periods.

SR 531 is a regionally significant highway located in developing urban growth areas in Snohomish County. This corridor serves traffic from Arlington and Marysville’s urban growth areas, both of which support industrial and commercial development, as well as unique limitations associated with an expanding airport facility. The highway links I-5 and SR 9, two highways of statewide significance. 

This area is planned as a regionally significant commercial/ industrial center. 

• Targeted development in this urban area is expected to increase employment by 90 percent in Arlington’s UGA and 71 percent in Marysville’s UGA by 2025. 
• Numerous parcels on the south side of the corridor currently used for agricultural purposes are zoned for general commercial development and are expected to accommodate a range of uses, including retail.
• In addition, Arlington is developing 126 acres at the southwest corner of Arlington Municipal Airport, between 43rd and 51st for the Arlington Airport Business Park.
• The city of Marysville also has an economic development plan for 1,859 acres that make up the Smokey Point Master Plan Area and Neighborhood which will also attract additional trips to this corridor.
  

The End Result
Our engineers believe that a roundabout is the best solution for improving safety and relieving congestion at the State Route 9/State Route 531 intersection in Arlington.

The roundabout will help prevent serious collisions for the 17,000 drivers that use the intersection daily. And it will work more efficiently than a signal as a significant amount of development occurs near the intersection.

Project Benefits

There are several reasons why roundabouts help reduce the likelihood and severity of collisions:

• Low travel speeds – Drivers must slow down and yield to traffic before entering a roundabout. Speeds in the roundabout are typically between 15 and 20 miles per hour. The few collisions that occur in roundabouts are typically minor and cause few injuries since they occur at such low speeds.
• No light to beat – Roundabouts are designed to promote a continuous, circular flow of traffic. Drivers need only yield to traffic before entering a roundabout; if there is no traffic in the roundabout, drivers are not required to stop. Because traffic is constantly flowing through the intersection, drivers don't have the incentive to speed up to try and "beat the light," like they might at a traditional intersection.
• One-way travel – Roads entering a roundabout are gently curved to direct drivers into the intersection and help them travel counterclockwise around the roundabout. The curved roads and one-way travel around the roundabout eliminiate the possibility for T-bone and head-on collisions.

What is the project timeline?

• Nov. 2012 - Complete construction
• May 7, 2012 - Begin construction
• Nov. 2011 - We awarded contractor Interwest Construction Inc. of Burlington the $5 million contract.
• July 21, 2009 - Open house: 6 to 8 p.m. at Arlington High School, 18821 Crown Ridge Blvd, Arlington.
• Oct. 2009 - pick improvement option
• Oct. 28, 2009 - Open house: 6 to 8 p.m. at Arlington High School, 18821 Crown Ridge Blvd, Arlington.
• Oct. 28, 2009 - Access hearing: 7 to 9 p.m. at Arlington High School, 18821 Crown Ridge Blvd, Arlington.
• 2012 - begin construction. 

Financial Information

Project signage will reflect the cost of construction engineering, project bid award and sales tax.

 

How can I get more information?
Contact:
 
Communications, Bronlea Mishler
1043 Goldenrod Road, Suite 101
Burlington, WA 98233-3415
Phone: 360-757-5997
E-mail: bronlea.mishler@wsdot.wa.gov  

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