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Budget Information

SR 99 - Automated Viaduct Closure Gates System - Complete June 2011

Project Status - Complete

This map shows the locations of all nine automated traffic control gates on State Route 99.

When the automated gate system is activated, a flashing sign warns motorists that the viaduct is closed.

Automated closure gate at the Columbia Street/southbound SR 99 on-ramp in downtown Seattle.

Crews testing "gate 8" at the northbound SR 99 Battery Street on-ramp.

WSDOT installed a system of automated traffic gates designed to safely close the Alaskan Way Viaduct within two minutes of detecting a magnitude-5 earthquake or higher - one strong enough to weaken the viaduct. The new system will be in place until a tunnel under downtown Seattle replaces the viaduct.

The new system consists of nine gates, similar to railroad crossing gates, located at all viaduct access points and controlled by an earthquake detection system.

When the earthquake detection system detects a magnitude-5 earthquake or higher, the system automatically signals all nine traffic gates to lower into place. Next, the system automatically notifies emergency responders, WSDOT's 24-hour traffic management center, SDOT and the King County Department of Transportation. 

How You Benefit
Cross GlyphImproves Safety
The automated viaduct closure system safely closes the viaduct to traffic after a moderate to severe earthquake with limited assistance from emergency responders.

Partnerships & Cooperation
WSDOT partnered with the Seattle Department of Transportation on this project. 


Financial Data for PIN 809936D
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $3,779
2005 Gas Tax (TPA) $151,209
Pre-Existing Funds (PEF) $195,985
Total $350,974

 $5.5 million

In September 2009, the federal government awarded WSDOT a $5.5 million highway funding grant. WSDOT used this funding to design and build the SR 99 Automated Viaduct Closure Gates System.

A portion of the total available funding was used to build a fiber optic communications network and hub, which will bring real-time traffic information to drivers on the roadway that replaces the Alaskan Way Viaduct.

Contact Us
Broch Bender, WSDOT Communications
Direct: 206-805-2817
Information line: 1-888-AWV-LINE (1-888-298-5463)

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