They reduce speeds, present fewer conflict points, allow for greater vehicle capacity, and have low maintenance costs. Parametrix staff designed the first modern roundabout on a Washington State highway (the Bethel Avenue roundabout) and recently opened two of the first multi-lane roundabouts in Lacey. We are currently in various stages of design for six other roundabouts in Thurston and Pierce Counties.

Parametrix also offers seminars on a range of roundabout topics. These seminars range from one day to three days depending on client's interest and needs.

Specific projects include:

• Marvin Road NE/ Willamette Drive - Lacey, WA
  The Marvin Road Corridor project consisted of roadway reconstruction/widening and new roadway construction of approximately 3,500 and 2,000 feet, respectively. Included in the design were two roundabouts along Marvin Road.
  
  One roundabout was designed to accommodate two additional approaches as access points to future commercial development along Marvin Road. The second roundabout location merges Marvin Road NE with the new Willamette Drive extension. This recently constructed roundabout is the first one built in this state that features dual lane approaches and exit lanes. Funding sources consisted of an LID, TIB grant, and city funds.
  
  
• SR 166/Bethel Avenue Wye - Port Orchard, WA
  The Bethel Avenue Wye was a triangle intersection of a city arterial with SR 166. Various traffic circle (roundabout) and traffic signal design concepts were evaluated for their ability to improve traffic flow and safety at this intersection with a high accident rate. The selected solution was the first modern roundabout on a Washington State Highway.
  
  This project involved a detailed grading plan to accommodate challenging intersecting grades. Steep grades were flattened to provide the desired approach gradient for all vehicle movements. Sight distance diagrams and illustrations were prepared to show that adequate sight lines would be achieved for the vehicles entering the roundabout.
  
  
• The Olympia Gateway Project - Olympia, WA
  Parametrix is part of a multi-firm team providing design services for the 4th/5th Avenue corridor improvements. The main portion of the project involves reconstruction and widening of the existing 4th Avenue Bridge to a three-lane facility, along with associated street and intersection improvements between the 4th Avenue Bridge and West Bay Drive. Parametrix is designing two roundabouts to relieve traffic congestion on the 4th and 5th Avenue corridor, where traffic is currently being funneled onto two older bridges, the gateway into downtown Olympia.
  
  
• 51st Ave./Burnham Dr. Roundabout - Gig Harbor, WA
  Parametrix staff designed the intersection roundabout of this major commercial development in the city of Gig Harbor. Project includes design of a modern roundabout at the main entrance into the development, along with associated storm drainage and pedestrian and bicycle connections. This roundabout is currently designed as a single-lane facility with the option of being converted to multi-lane in the future, as dictated by traffic volumes. The roundabout geometry was established using SIDRA capacity analysis software. Challenges include a steep approach grade and matching into existing roadways and driveways, both horizontally and vertically.