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SE 43rd/East Lake Sammamish Parkway Intersection Improvements

Summary

The city of Issaquah is currently pursuing improvements to the intersection of East Lake Sammamish Parkway and SE 43rd Way to improve traffic safety and traffic operations. This project is associated with the Mallard Bay residential development located on the northeast and southeast corners of the intersection. This development was approved by King County and requires traffic mitigation improvements to the intersection that involve a traffic signal upgrade and widening along SE 43rd Way. The City of Issaquah is working with the Developer to consider constructing a roundabout in place of the signal revision.

In conjunction with the city of Issaquah, The city of Sammamish hired a consulting engineering firm to perform a feasibility study to determine if a roundabout is appropriate for this location. The results concluded that a roundabout would greatly outperform a traffic signal. A link to the Consultant's Technical Memorandum is included below.

City of Issaquah staff are currently working on a agreement with the developer to build the roundabout which could begin construction later this year.

Resources

• Final Tech Memo: 1066 KB
• Conceptual Layout: 685 KB
• 2022 Peak Hour Forecast Queue Lengths
  • Roundabout AM Peak Hour: 649 KB
  • Roundabout PM Peak Hour: 652 KB
  • Traffic Signal AM Peak Hour: 594 KB
  • Traffic Signal PM Peak Hour: 559 KB
• Status Report - Insurance Institute for Highway Safety Newsletter
  • Roundabouts reduce traffic backups as well as crashes involving injuries (July 28, 2001): 227 KB
  • Roundabouts are becoming more familiar on U.S. roads, not just for safety reasons (May 13, 2000): 396 KB
• 2022 Peak Hour Simulations - Computer simulations showing how the proposed roundabout would operate with traffic forecast for the year 2022. NOTE: The simulations are shown at 2x actual speed. Simulation files require Windows Media Player.
  • AM Peak Hour (view from the south): 2.33 MB
  • PM Peak Hour (view from the south): 2.37 MB
  • AM Peak Hour (view from the north): 1.36 MB
  • PM Peak Hour (view from the north): 1.32 MB

News releases

Staff Contacts

• City of Sammamish: Jeff Brauns, Senior Transportation Program Engineer, (425) 295-0561;
• City of Issaquah: Gary Costa, Transportation Manager, (425) 837-3443.