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I-5 Variable Speed Limits and Lane Control, Washington State


The project covers a 7-mile long section of I-5 northbound in Seattle and was activated August 10, 2010.

  • 15 overhead gantries, spaced approximately ½ mile apart through the 7-mile project area.
  • Gantries display dynamic speed limits, lane closures, merge arrows, warning information and variable messages.
  • Speed adjustments are automated and based on measured changes from imbedded sensors.
  • Lane control changes are human-initiated, but software automates the process of updating the signage and messages.
  • Variable speed limits sign show a minimum of 40 mph, even if traffic is moving slower.
  • Project has potential to improve congestion and safety

Operations Area of Practice

    Active Traffic Management (ATM)

Organizational Capability Element

    Active Traffic Management/Travel Demand Management/Pricing

Content Type

Case Studies & Lessons Learned

Publishing Organization

SHRP2 Program


Available Tools

Document Downloads

Prime Contractor
Kittelson & Associates
TOM Chapters
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