Seattle traffic signal engineers have plan for viaduct closure

    Seattle traffic signal engineers have plan for viaduct closure (PHOTO: KOMO News)<p>{/p}

    No doubt, you’ve said to yourself "why can’t they time the signal lights better."

    When the viaduct closes for good and Seattle endures a loss of a major north-south thoroughfare for three weeks, the city’s traffic signal engineers say they have a plan.

    “It’s a very vulnerable, touchy-like system, it works as a puzzle, where when you take one piece away, you may have unintended consequences,” says Adiam Emery, Transportation Operation Center Manager.

    On the 37th floor of Seattle’s Municipal Tower, in a room with computers and a wall of video monitors of traffic cameras, the Seattle Department of Transportation is preparing its plans for keeping the traffic flowing.

    “There will be signal timing engineers and adjusting things as we see fit,” says Emery. The operations center has 300 traffic signals under their control.

    The team has come up with 1,800 models based on historical traffic jams including the closure of the viaduct for 10 days in 2016. A traffic engineer can make adjustments to the timing of one intersection or several at once instantly. Any adjustment could make things better or worse.

    So an engineer, without altering the timing of a signal, can run one of the 1,800 models to see if that model could improve the situation on the ground. If the engineer believes it can, the model could be implemented with a touch of a computer mouse and that sector of signals could change.

    What SDOT found out during the 2016 closure was drivers tended to reroute themselves off Highway 99 just north and south of the city and headed to I-5 which became gridlocked. SDOT found a 50 percent increase over a typical workday in SODO and South Lake Union neighborhoods.

    In the South, on and off ramps at Dearborn and Edgar Martinez way were jammed. In the north, Mercer Street and Denny Avenue were clogged with traffic trying to get to and from I-5, while the streets in downtown ran lighter than expected.

    “So the choke point that we will be facing is if I-5 is at capacity," Emery said. "Then you will see the back-up coming onto city streets."

    If you have to drive into downtown, a helpful hint will be to follow the buses.

    “Our hierarchy of priorities are to move transit as fast as we can and increase reliability,” says Emery. Second on that list is making sure that other streets that feed I-5 are flowing smoothly.

    And thirdly, is to keep traffic flowing in the north-south routes through downtown because the viaduct was a north south route.

    Emery says it’s time to practice patience.

    “Be patient, it works as a network. Any little thing can impact the flow of it, but we are here to try and make sure to keep things moving."

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