SDOT preparing for Seattle Squeeze

Seattle’s “Period of Maximum Constraint,” when large construction and transportation projects cause traffic congestion to peak, is coming up fast. The transportation department is ramping up its response now, to ensure resources are quickly deployed when the time comes.

SDOT upgraded its Transportation Operations Center to a 24/7 system in October, monitoring traffic flow around the city and deploying aid where needed; it had originally only operated from 6 a.m. to 10 p.m. daily.

Following a three-year pilot program, the SDOT Response Team also became a 24/7 tool for clearing traffic impacts and keeping vehicles moving throughout the city.

Those incidents include collisions, disabled vehicles, potholes, special events, when the Ballard Bridge gets stuck, and fallen trees, which Transportation Operations Center supervisor Tim McCall said can occur in the downtown area due to new office and residential towers creating wind tunnels.

“And that’s been the case in South Lake Union recently,” he said.

The SDOT Response Team was deployed to 446 incidents during regular hours between Oct. 1-29, and three-fourths of those were collisions, McCall said. Seventy-six were for disabled vehicles, and then there were nine traffic signal outages and five special events to manage.

Moving to a 24/7 operation, the center now has overnight data, McCall said, which shows 62 responses in that same October timeframe, with three-fourths again being for collisions.

There are a number of factors that will contribute to Seattle’s “Period of Maximum Constraint,” or what SDOT is now calling the “Seattle Squeeze.” The city expects more than 200,000 new jobs to be created in Seattle by 2020. The planned closure of the Downtown Seattle Transit Tunnel in March will push 40 buses per hour during peak times on to surface streets. The Washington State Convention Center’s works on its Addition project led to the closure of the Convention Place Station’s closure in July.

But the first major traffic headache in 2019 will be the three-week closure of the Alaskan Way Viaduct starting Jan. 11, so WSDOT can create a new link from State Route 99 to its recently completed SR 99 Tunnel. WSDOT reports 19,000 vehicles use SR 99 daily.

Many people are expected to use the new tunnel when it opens, but WSDOT will eventually implement a toll schedule approved last month by the Washington State Transportation Commission, which McCall said is expected to cause a substantial number of drivers to seek alternative routes to get around it.

Vehicle activity is expected to increase north and south on Second Avenue, north on Fourth Avenue and south on Fifth Avenue. There will also be impacts from Third Avenue downtown now being transit-only from 6 a.m. to 7 p.m. every day, McCall said.

SDOT is making traffic signal changes now, with some changes to frequency expected as the transportation department sees need.

SDOT community engagement liaison Dawn Schellenberg added that a companion project for the new SR 99 tunnel will be reconnecting Harrison, Thomas and John streets to Aurora Avenue. Harrison will open up the same time as the tunnel, but John and Thomas could take up to 16 months, according to an article by the Puget Sound Business Journal.

McCall said there is a team of signal engineers working on an adaptive system in the Mercer corridor.

“The downfall is the freeway (Interstate 5) can only accommodate a number of vehicles,” he said.

There are more than 600 traffic signals in Seattle, and SDOT has the ability to adjust them in real time from the Transportation Operations Center when incidents arise.

Mayor Jenny Durkan said a request will be made to the Legislature to allow for ticketing drivers who block intersections, as often occurs on Mercer Street during peak traffic periods. Police currently must witness a blocking violation, and stopping vehicles for ticketing only causes more congestion. The request to the Legislature would be to have the ability to track those incidents with enforcement cameras. The Seattle Police Department monitors cameras for speeding and running stop lights, and would also be in charge of potentially tracking block-the-box violations.

The Transportation Operations Center currently has a staffing level of three during the day, two in the evening, and then one overnight, McCall said, and there could be adjustments in the future if needed.

People can check road congestion conditions at seattle.gov/travelers. More Seattle Squeeze resources are available at the recently launched seattletraffic.org website.