Report: Pine, Argonne interchange upgrades would improve Valley traffic flow

Chances are you will never reach the posted 35 mph speed limit on Argonne Road between Mission and Trent avenues. A traffic study almost completed by the public works division of Spokane Valley shows that most drivers travel at speeds between 10 and 12 mph on that stretch, making it one of the most congested areas in Spokane Valley.

“About 42,000 vehicles travel over the two-lane bridge at Argonne every day,” said Sean Messner, senior traffic engineer with Spokane Valley, “bringing us very close to capacity there.”

The University Road Overpass Study focuses on what it would take to remedy two very congested areas in Spokane Valley – the Argonne interchange and the Pines interchange – and whether constructing an overpass at University Road, spanning I-90 and the railroad tracks, would make a difference.

The short answer is no.

“We did look at connecting University with a bridge,” Messner said, “but it did not lessen congestion at Argonne and Pines.” Messner said the neighborhood between Pines and Argonne remains divided by I-90, however, and a bicycle and pedestrian bridge, perhaps with emergency vehicle access, certainly would be great for the neighborhood.

“Around 400 people would use a bridge like that every day,” Messner told the Spokane Valley City Council during his presentation Tuesday evening.

Around 32,000 vehicles pass through the interchange at Pines and I-90 every day.

Making a southbound turn onto Pines from I-90 can be especially complicated during rush hour. Not only are the traffic lights at Indiana and Mission avenues very close to the off-ramps from I-90, but that’s also the part of Mission with the highest traffic volume, Messner said.

“That’s why it’s a chokepoint,” Messner said. “And the hospital is right there, too.”

At Argonne, there are six traffic signals within three-quarters of a mile. Messner said though traffic engineers try to coordinate them, it’s almost impossible to make a green wave because there’s so much traffic.

“You are bound to get stuck at a red light somewhere,” Messner said.

The study identified 16 options for reducing congestion at Argonne and Pines. Those options were narrowed down to nine, and Messner shared the staff recommendations with the City Council.

The preferred option for the Argonne corridor is to expand the southbound Argonne bridge to three lanes; the northbound Mullan bridge already has three lanes. That would cost $6 to $9 million, Messner said.

At Pines and Mission, minor changes to traffic signals and longer turn lanes would improve traffic flow significantly, Messner said, adding that could be done for between $200,000 and $400,000.

Finally, a bicycle and pedestrian bridge running north-south along Mission Park and crossing both I-90 and the railroad would cost $4.5 to 6 million, Messner said.

Mayor Dean Grafos was surprised that a University overpass with car access wouldn’t relieve congestion. Messner explained that to be really effective, a University overpass would have to connect to I-90.“Without the on and off ramps it will not make much of a difference,” Messner said.

None of these projects has any funding.

To be funded, the City Council first has to approve the project – or projects – and then add them to the Spokane Valley Transportation Improvement Plan, and on to the State Transportation Improvement Plan.

“It has to be in the state plan to get federal funds,” Messner said.

The next round of federal funding is expected to be available in 2020.