Seattle’s SR 99 tunnel route finally fully open, faces full traffic

Seattle commuters are watching closely to see how well the new SR 99 tunnel works as the passage comes fully online. With a new exit ramp to Dearborn Street open Tuesday morning, many wonder if backups will continue inside the new tunnel.

WATCH: A test drive through Seattle’s new tunnel
RELATED: First day with Seattle’s new tunnel

KIRO Radio Traffic Reporter Chris Sullivan notes that the new SR 99 tunnel backed up slightly out of the tunnel Tuesday morning, around the Seattle’s stadiums.

“But that’s nothing like before (without the Dearborn exit) when traffic was backed up to the West Seattle Bridge,” he said. “But there was a little slowing, especially in that 8 a.m. hour.”

The tunnel loses about a third of capacity from the defunct Alaskan Way Viaduct. Sullivan says that could be a cause of some slowing through this area.

The planned Viadoom, and the unplanned snowstorms that hit Western Washington, have kept heavy traffic off area roads as Seattle’s new SR 99 tunnel came online over the past couple weeks. When the tunnel did open in early February, a backup formed out of the two-mile passage — stretching nearly four miles. Still, the full route wasn’t operational, as one exit to Dearborn Street at the south end was not yet open.

That exit opened Tuesday morning. With no snow or other road-snarling factors, traffic experts like KIRO Radio Traffic Reporter Chris Sullivan were paying extra close attention to tunnel traffic. Sullivan noted that the tunnel seemed smooth during the early commute.

“Seems to be working well,” Sullivan said around 7:45 a.m. “I’ve been watching the Dearborn off ramp, people are using it. It’s making the drive a little easier through the tunnel.

But by 8:15 a.m., things were changing.

“We’ve got off-and-on backups from the stadiums, all the way through the north end,” he said. “Even though we have both exits open today, I think we might be looking at our first real day of traffic … this is our first real commute without the snow and operating at normal capacity.”

“Still seeing heavy slow downs through the tunnel, northbound, trying to get off at the north end,” Sullivan said a short time later. “We are seeing the backup starting right at the Dearborn interchange. I guess that’s our new normal.”

For the first time this morning, there is slowing NB 99 into the new Seattle tunnel. First day with Dearborn exit open. pic.twitter.com/uG1gatGtyx

— KIRO Radio Traffic (@KIROTraffic) February 19, 2019

SR 99 off ramp to Dearborn Street

The new off ramp from SR 99 to Dearborn Street at the south end of the tunnel is more than meets the eye. It may seem like a regular ramp, but it’s actually the first of its kind.

According to the Washington State Department of Transportation, “This ramp is the first in the world built with flexible metals and bendable concrete designed to sway with a strong earthquake and return to its original shape. Its innovative design has won regional and national recognition.”

The ramp will therefore withstand the heavy shocks from a major earthquake. WSDOT further states:

This pilot project is the first real-world test of 15 years of research inside the Earthquake Engineering Lab at the University of Nevada, Reno – one of the top earthquake engineering laboratories in the U.S.

Modern bridges are designed not to collapse during an earthquake, but this new technology takes that design a step further. In earthquake lab tests, bridge columns built using memory-retaining nickel/titanium rods and a bendable concrete composite proved more flexible. The columns were able to return to their original shape after an earthquake as strong as a magnitude 7.5.

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