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SR 150 - No See-Um Road Intersection Improvements Alternatives

After six years of analysis, two alternatives to address the congestion and safety issues associated with the No See-Um Road intersection remained.

One was to construct left turn lanes and a right turn pocket on SR 150, relocate the intersection to the west, tie in Spader Bay Road as the south leg and relocate SR 150 to the south. 

The final choice was construction of a roundabout at SR 150 and No See-Um Road west of the existing intersection that would include Spader Bay Road tieing in from the south. 

Roundabout Alternative

  • Advantages - fewer conflict points at the intersection and no left turn conflict points; reduced wait times on side streets; reduced collision severity; reduced annual maintenance expenses. 
  • Disadvantages - slows SR 150 traffic to below 25 mph; property impacts on south side of SR 150. 
  • Collisions - addresses all types of collisions.  Reduces injury collisions by 70%. 

An inherent design feature of roundabouts is that they eliminate high speed left turn and right angle conflicts which are the ones that result in the most serious "T bone" collisions.

According to the Insurance Institute for Highway Safety , roundabouts have been shown to reduce fatal collisions by 90 percent, injury collisions by 80 percent and total collisions by almost 40 percent.

Something you may not know about roundabouts involves how trucks get through them properly courtesy of what’s called a truck apron. That’s the raised, circular concrete part around the center of a roundabout. It acts like an extra lane for large vehicles. So when you’re driving a roundabout, and see a trailer riding up on that raised concrete circle, don’t worry. That’s what it’s there for. (See the pictures and video ). To learn more, watch “ how do I drive a roundabout video ” on YouTube and visit WSDOT’s roundabout website .