In general, the state Department of Transportation prefers to install roundabouts versus other intersection types. (WSDOT)

In general, the state Department of Transportation prefers to install roundabouts versus other intersection types. (WSDOT)

How and why an intersection gets redesigned in Washington

The most common question submitted to Street Smarts: How do I get a roundabout installed?

Emails about intersections Street Smarts readers find treacherous have begun to accumulate in my inbox. Drivers want to know how they can get an intersection redesigned.

Just recently, I heard from Everett Lewis, who wanted the state Department of Transportation to re-evaluate the intersection of Highway 530 and 211th Place SE. He said drivers speed down 530 making it difficult for vehicles trying to turn left from 211th.

Lewis recommended installing a roundabout there, which he said could help reduce accidents and slow speeds as population growth continues to explode in that area.

Will Brandt also proposed a roundabout where Highway 9 and Highway 92 cross in Lake Stevens. And he took issue with where 60th Street NE crossed the highway.

These are just a few of the emails wanting to know how to catch WSDOT’s attention about a particular intersection. Instead of inundating WSDOT with all the requests and waiting for answers, many of which would likely disappoint the traveler, I thought I’d walk through the transportation agency’s procedure for considering whether an intersection needs to be redesigned, known as an Intersection Control Evaluation report.

A variety of things can trigger this five-step analysis, including a request from the public or elected leader. Or a history of safety or operational issues. A new development can also start the process.

“The purpose of completing an Intersection Control Evaluation report is to ensure the change fully addresses the long-term need in a cost-effective manner,” said Joseph Calabro, a spokesperson for WSDOT.

Intersections aren’t required to have a certain volume of cars or crashes to begin the review, he said.

Step 1. After an intersection is selected for the evaluation, data on traffic volumes and how vehicles move through the intersection is collected. The agency looks at all possible alternatives based on the need and site conditions.

A goal for a redesigned intersection is also established at this point.

Step 2. In this phase the feasibility of the designs are evaluated. A sketch of each potential project is done to determine the space required and if any environmental risks exist.

Step 3. WSDOT then uses a computer to model current and future traffic conditions under the alternative designs being considered to evaluate how each would operate.

Crashes and causes over the last five years are also analyzed. Designs are run through a traffic safety computer model that predicts if accidents would be reduced.

A scenario where no changes are made is also studied.

Step 4. The alternatives are measured against each other. This includes comparing cost estimates, savings in travel times and how each meets the goals set out in step 1.

Step 5. A recommendation is selected.

In general, WSDOT’s preference is to install roundabouts when possible, Calabro said.

“Roundabouts are proven to be the safest for motorists and pedestrians,” he said.

The public is also given a chance to comment. In general, when that is done, several designs are put forward.

Funding then probably needs to be secured before anything actually happens.

Got a question? Email me at or call 425-374-4165. Please include your name and city of residence.

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