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Adapting to Mercer Street

We recently launched a new signal timing system along the Mercer corridor, an ‘Adaptive Signal System’ called SCOOT, which uses algorithms and sensors to adjust signal timing to adapt and respond to real-time traffic conditions.

SCOOT in action.

SCOOT was installed on Mercer St from 3rd Avenue W to Fairview Avenue N (at I-5) and on the parallel streets of Roy and Valley. Since the launch, we’ve received a lot of feedback so we thought we’d answer some questions.

  1. Why do pedestrian signals not automatically bringing up a “walk” sign?

SCOOT is designed to improve traffic flow by adapting to current conditions. Displaying a “walk” signal during every light cycle, whether there are pedestrians there or not, would be inefficient and slow down every other mode of transportation, including pedestrians crossing on adjacent streets.

While we have detectors for vehicle, transit, and bike traffic; we don’t have a way to detect pedestrians who are waiting to cross the street – unless they use the pedestrian push buttons. That’s why it’s important for pedestrians to actually push the button – to let the system know they are waiting to cross. We are looking at pedestrian detection technologies that might eliminate the need for push buttons in the future.

  1. Why is the crossing time shorter for pedestrians? And, why does it not stay on “walk” the whole time the parallel vehicle movement is “green”?

The “walk” display time was shortened to improve overall traffic flow as part of SCOOT, though the minimum necessary time to cross is still provided whenever a person pushes the button to cross. This minimum time is a combination of the “walk” time and the flashing “don’t walk” time – with the total based on a walking speed established by the US Department of Transportation. We are actively reviewing signal data to continue to adjust walk times.

Although the amount of time to cross Mercer may be shorter with SCOOT, pedestrians actually have more opportunities to cross Mercer. This is helpful in areas such as on Valley Street between Westlake Ave N and Fairview Ave N, where there are high volumes of pedestrian traffic going back and forth from South Lake Union.