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SR 99 Tunnel Project
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How traffic will work after Seattle’s SR 99 tunnel opens


Seattle’s SR 99 tunnel is going to bring major changes to traffic in downtown Seattle when it opens in early-2019.

RELATED: How much it will cost drivers to use Seattle’s new SR 99 tunnel

The Washington Department of Transportation was quick to point out in a recent blog post that while Seattle’s issues with traffic are significant, the tunnel is a “safety project, not a congestion-relief project.” The main goal behind replacing the viaduct has always boiled down to the risk posed by an earthquake.

So how will the tunnel benefit drivers directly? WSDOT noted that the “the tunnel will be a more direct route for drivers who want to get through downtown.” While the current viaduct features ramps downtown at Seneca St., Columbia St., and Western Ave., the tunnel will streamline down to a pair of entrances and exits in South Lake Union and SoDo.

SR 99, before and after the tunnel project


The hope is that once Alaskan Way surface street improvements are completed in 2021, traffic patterns will settle. The idea is to have the surface streets offset the restrictive nature of eliminating downtown ramps.

“The new Alaskan Way is designed to work with the tunnel and give drivers multiple options to get into and through downtown,” said WSDOT.

Will people actually use the tunnel?

According to WSDOT, “traffic predictions show that before tolling begins, there will likely be more drivers using the tunnel during peak periods than use the viaduct today.” Currently, over 5,000 people use the viaduct every day, while initial estimates for the tunnel account for 7,000 daily drivers.

The tunnel will initially be toll-free, before opening up to tolling in summer 2019. Once that occurs, the expected amount of daily vehicles will drop from 7,000 to somewhere between 4,000 and 5,000.

Tolls were recently set at $1 for weekends and overnight, between $1.25 and $1.50 during the morning commute, and up to $2.25 for the peak rush hours between 3-6 p.m.

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