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.
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
||Amount ($ in thousands)
|2003 Gas Tax (Nickel Funding)
|2005 Gas Tax (TPA)
|Pre-Existing Funds (PEF)
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.
Broch Bender, WSDOT Communications
Information line: 1-888-AWV-LINE (1-888-298-5463)
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