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I-5, I-205 bridge crossings to and from Clark County plummet early on during pandemic

Traffic numbers on the Interstate 5 Bridge and Interstate 205 Bridge plummeted during the early weeks of the coronavirus pandemic, with daily vehicle crossings on I-5 dropping from a weekday average of about 139,000 in the first week of March to about 85,000 at the start of April.

The numbers reflect a large-scale shift in commuting patterns as thousands of Clark County residents with Portland jobs made the switch to working from home.

Daily crossings have begun to climb again, but local transportation officials have an important message for participants of the Great Telecommuting Experiment of 2020: Be ready to do it again.

Clark County is about three months out from the start of the I-5 Bridge trunnion replacement project, which will relegate all of the freeway’s traffic to the southbound span for up to nine days while the northbound span undergoes an extensive renovation of its lift mechanism.

The last trunnion repair project was in 1997, and Clark County’s population has grown significantly since then. The traffic impacts are expected to be severe, and transportation officials have spent years warning drivers and employers to plan in advance and develop strategies to avoid peak commute hours.

However unintentionally, the coronavirus pandemic may end up serving as a sort of dry run.

“One of the things we have seen recently is a workforce that is becoming more accustomed to working from home, and those habits may serve travelers very well when we come to the closure in September,” said Oregon Department of Transportation spokesman Don Hamilton.

Large early declines

The traffic impacts at the peak of the pandemic were striking; after Gov. Jay Inslee’s stay-at-home order took effect in late March, traffic at key counting points across Washington dropped by almost half, according to Washington State Department of Transportation spokeswoman Kimberly Pincheira.

Traffic counts in Clark County near the state border dropped by 30-40 percent on weekdays and 40-50 percent on weekends, she said.

ODOT data shows similar impacts on the freeway bridges. With the exception of New Year’s Day, weekday crossing totals ranged from about 125,000 to 149,000 on the I-5 Bridge and about 149,000 to 175,000 on the I-205 Bridge from the start of 2020 through March 13.

The tipping point was the weekend of March 14. The following Monday, daily crossings on the I-205 Bridge dropped to 138,104 — more than 10,000 fewer crossings than on any prior nonholiday weekday in 2020. On the I-5 Bridge, crossings dropped to 119,226.

Traffic declines continued almost daily for the next two weeks. Weekday crossings for both bridges bottomed out on March 30 with 80,121 crossings of the I-5 Bridge and 88,451 crossings of I-205 Bridge. The numbers began to climb again after that point, but at a much slower rate than the initial decline.

Mid-April traffic on the I-205 Bridge was still down about 40 percent compared with the same time period in 2019, according to a June 5 ODOT report on the regional traffic impacts of COVID-19. Mid-April traffic was down about 30-35 percent on the I-5 Bridge compared with the same time in 2018.

By the first week of June, traffic levels on both bridges had risen to between 19 and 24 percent below their normal totals, depending on the bridge and the direction of traffic. WSDOT data shows a similar recovery for Clark County traffic near the border, Pincheira said, with traffic currently down by about 20 percent on weekdays.

“The pandemic has been the most significant change in traffic that we’ve seen in my lifetime,” Hamilton said. “Traffic usually changes only gradually, and here we saw a dramatic change in just a matter of a few weeks.”

Trunnion preparations

With the pandemic still very much ongoing after three months, it’s tempting to wonder if the reduced traffic levels might carry through to September and mitigate the need for further action during the trunnion project.

Don’t count on it.

“It’s safe to say that we don’t know what the traffic levels will be when we get to (the start of the closure period on) Sept. 12,” Hamilton said.

Traffic levels have already recovered significantly from the early April low point. They’ve continued to trend upward in recent weeks, although the ongoing nature of the pandemic continues to make it difficult to predict what traffic will look like three months out.

But even if the current pattern changes, there’s a second reason why the pandemic likely won’t mitigate the impacts of the trunnion project, Pincheira said: Rush-hour traffic didn’t decline as much as traffic during the rest of the day. Even at its lowest point, peak-hour crossings weren’t that far below the level where jam-ups tend to start to form — and that’s with both bridge spans operational.

“When traffic levels were at their lowest during the pandemic, we only saw a 20-25 percent drop in traffic during the morning peak hours,” Pincheira wrote in an email. “So even when we saw traffic volumes at their lowest during this pandemic, it was not enough of a drop to avoid major traffic impacts during the trunnion repair work.”

ODOT plans to step up its public outreach during the final months leading up to the project, particularly in Clark County. The message will be to expect heavy congestion and plan accordingly — including by incorporating any lessons learned during the pandemic about working from home.

“Everyone can help reduce congestion during the closure by using options such as delaying or shifting trips, biking, taking transit, or working from home or another location when possible,” Pincheira said in an email.


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