Drivers getting used to new Salmon Creek Interchange

Almost a month after the opening of a new freeway interchange at Northeast 139th Street, traffic patterns in the Salmon Creek area still appear to be in flux as thousands of drivers feel out the new setup.

But regular commuters should find a new normal soon, county and state transportation officials say.

“I think we’re getting closer,” said Rob Klug, Clark County’s traffic signal operations and engineering lead.

For now, “there’s a lot of variability in the traffic out there,” he said.

The new interchange and bridge at 139th Street opened to much fanfare on Aug. 27. A ribbon-cutting ceremony to mark the occasion ended four years of construction, and came 17 years after planning began on the $133 million Salmon Creek Interchange Project. The effort also rebuilt local roads and made improvements to Interstate 5 and Interstate 205 near the convergence of the two freeways.

New patterns develop

Nearby Northeast 134th Street, long plagued by congestion and backups, has seen a marked improvement since the new interchange opened, according to county traffic data. For example: The offramp connecting northbound I-5 to 134th Street once carried about 12,000 vehicles per day, Klug said. Now, more than a third of that traffic — 4,500 vehicles per day — uses the new northbound offramp at 139th Street, he said.

Other ramps at 134th Street have seen similar improvements, said Bart Treece, a spokesman with the Washington State Department of Transportation. In general, the new interchange and improvements are performing well, he said.

Earlier models predicted that as much as 40 percent of the traffic at 134th Street would shift to 139th Street, Klug said. Depending on where it’s measured, that number is around 25 percent to 33 percent so far, he said. But that may change as drivers continue to adjust.

“People are still learning their way around, and it takes a while to break habits that they’ve had for a very long time,” Klug said.

Clark County is still working on the timing of traffic signals to best move traffic safely and efficiently through the area, Klug said. That’s a complex process involving a lot of factors, and the county has used cameras among other tools to monitor conditions. Klug himself lives in the area and drives the new interchange regularly, he said.

The county has measured about 6,000 vehicles per day on 139th Street west of Northeast 10th Avenue. The intersection of those two streets is one place where some drivers have reported backups at times since the interchange opened.

Until a new facility actually opens, predicting how it will function can be a challenge, Klug said.

Overall, “it seems to be working very well from our perspective,” he said.