City engineers recently reconfigured signal timing at some intersections along the busy street to allow pedestrians more time to cross during rush hours.

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Look both ways, move fast and hope for the best — that’s the strategy some pedestrians resort to while crossing Seattle’s Mercer Street with a traffic-light system they say cuts walking time too short.

Jennifer Wah, of Capitol Hill, wrote to Traffic Lab, describing frightening times crossing Mercer with her cousin at Fourth Avenue during the pair’s seasonal outings to ballet performances at McCaw Hall.

Wah’s cousin has arthritis in her knees and only makes it about halfway across Mercer before the “don’t walk” sign starts flashing, she said.

Traffic Lab is a Seattle Times project that digs into the region’s thorny transportation issues, spotlights promising approaches to easing gridlock, and helps readers find the best ways to get around. It is funded with the help of community sponsors Alaska Airlines, CenturyLink, Kemper Development Co., Pemco Mutual Insurance Company, Sabey Corp., Seattle Children’s hospital and Ste. Michelle Wine Estates. Seattle Times editors and reporters operate independently of our funders and maintain editorial control over Traffic Lab content.

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“I can make it because I can walk fast,” Wah said. “It’s still an effort to make it across knowing that the time is so short.”

In today’s column, we’re giving a rundown of signal timing in the hectic corridor, including a recent switch by the Seattle Department of Transportation (SDOT) to make some pedestrian-crossing times during rush hours longer — a change the department hopes will quell complaints.

“I’m an able-bodied fast walker and I have never been able to make it comfortably across Mercer without feeling endangered by impatient cars who cut me off,” one person recently tweeted to SDOT.

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First, let’s review Mercer’s signaling system.

Eighteen intersections on Mercer, as well as 10 on Roy Street, three on Republican Street and one on Westlake Avenue, are the first in Seattle equipped with an adaptive signaling system that uses sensors to pick up real-time traffic conditions and adjust lights accordingly.

The system, installed in April, aims to move vehicle traffic more quickly along Mercer, where about 60,000 cars a day vie for space between Interstate 5 and the Uptown neighborhood, also known as Lower Queen Anne. So far, SDOT says it is working.

Before the new signaling program, drivers spent up to 34 minutes going the length of Mercer to I-5’s onramps during particularly bad evening commutes (between 6 and 7 p.m.), SDOT reported in November. Now, those heavily congested trips take about 17 minutes on average.

In addition to the worst commutes improving, average travel times between 5 and 7 p.m. are shorter, too, with travelers spending about 10 minutes less in traffic.

But the challenge of adaptive light systems is keeping traffic flowing without making pedestrians wait too long to cross the street.

The system requires pedestrians to call for a walk signal by tapping a push-to-walk button at each intersection, rather than the lights changing solely on a timed schedule.

Walk times along the corridor vary by location, as do the lengths of the flashing “don’t walk” signs, which signal when pedestrians should no longer begin crossing.

Responding to pedestrians’ complaints, SDOT recently reprogrammed the system at 13 intersections so people have more time to cross during rush hours.

The increases vary by location, ranging from an extra four seconds at Taylor Avenue near the Bill & Melinda Gates Foundation headquarters to 22 seconds at First Avenue West on the west end of Uptown. Engineers made similar adjustments over the summer, increasing walk times.

It is unclear if, or to what extent, the recent tweaks have made a noticeable impact on pedestrians or cars.

After the changes in the summer, SDOT did a two-week study that found the longer walk times did not slow cars, according to the department.

“We want cars to be able to get through and on to I-5 as efficiently as possible, while giving pedestrians safe and reasonable walk times,” SDOT spokeswoman Mafara Hobson wrote in an email. “Over calibrated walk times for pedestrians will revert vehicular traffic back to the infamous ‘Mercer Mess,’ and no one wants that.”

The department, she added, is concerned about pedestrians feeling unsafe and continues to monitor the corridor for potential changes in the future.

Over the next several years, SDOT plans to install adaptive traffic-light systems on Denny Way and some intersections near Seattle Center and South Lake Union.

The roughly $4 million spent on Mercer’s signal-timing systems followed a half-decade of construction on the corridor that cost more than $260 million and brought two-way traffic, bike lanes and wider sidewalks.

But congestion persists, as the corridor takes the brunt of Seattle’s exploding growth with the neighborhood’s tech powerhouses Amazon and Facebook expanding. Construction on Google’s new complexes, between Terry and Fairview avenues North on Mercer Street, is now underway.

Jeff Ban, an expert in transportation-signaling systems at the University of Washington, emphasized a broad look at the city’s traffic problems, including those on Mercer, saying they reflect a growing population and economy.

“Tuning the signal systems could make things a little better but may not completely solve the issues,” he said.

Got an idea, question or suggestion for Traffic Lab?

Last week, we sat down with the guy in Seattle who helps connect investigators across the U.S. and Canada with Uber’s data to solve crimes. The week before, we spotlighted the new path for walking and biking on Highway 520’s floating bridge, set to open Dec. 20, the state announced Friday.

If you have a question or idea for us, send it to trafficlab@seattletimes.com. We may feature it in an upcoming column.