WSDOT caught off guard by success of I-405 shoulder driving

We’re more than a week into the shoulder driving program on I-405, and I owe the Washington State Department of Transportation an apology. It looks like this is actually having a big impact on the daily northbound drive out of Bothell.

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I was sure this wouldn’t do much for the daily grind through Bothell and Canyon Park because the location of the shoulder driving was too far away from where the freeway decreases from five lanes to three. But I was wrong.

Travel times improved significantly, and the average tolls also dropped during the first week of operation.

Kim Henry is in charge of the I-405/SR 167 improvement program, and he said giving a dedicated lane to about 1,000 cars an hour getting on I-405 northbound at Canyon Park in the afternoon has really made a difference.

“All the traffic has been able to continue into the new lane without having to merge in and break down the flow of traffic that was already continuing through the area, and that’s just caused the whole area to smooth out and get substantially better,” he said.

For example, the average general purpose lane travel time between Bellevue and Lynnwood during the afternoon peak was about 40 minutes during the first four months of the year. It was close to 20 minutes faster, on average, last week.

It’s not just WSDOT saying that. KIRO listeners are saying it too.

Bree asked: “Has the drive ever been 55 miles per hour at 5 p.m. in Bothell? Noooooo. This is amazing.”

Steven wrote us: “I used it all last week. Why don’t we have this on all of our roads?”

The success even caught Henry off guard.

“We were expecting to see much better performance, but this is really exceeding our expectations so far.”

But is this really a reality? We didn’t have any major accidents on that stretch in the afternoon last week. The weather was reasonably dry. Traffic volumes were also a bit lower than usual.

“It’s still very early, and we may have slightly little traffic volumes than typical,” he said. “Things might change over time.”

But the initial roll-out has been successful, and Henry said WSDOT is looking for any other ways to improve the corridor.

“I wish we had other places in the corridor where we could see this same type of benefit,” he said. “I think this is a very unique location and situation where we could make this work.”

It wouldn’t make sense or provide many benefits, Henry said, to add shoulder driving in this stretch in the southbound direction. Not enough drivers exit at Canyon Park and they would just have to merge back in, creating another chokepoint on the corridor.

The only solution to the entire corridor is to widen I-405 between Bothell and Lynnwood. The Legislature hasn’t funded that part of the program but did recently approve money for initial engineering.

The one negative impact of this shoulder driving is at the far north end, where it goes away. Henry says there is a little more congestion at the I-5 interchange, and traffic engineers are watching that.

Tell Chris about a Chokepoint or ask a traffic question @kirortraffic via Twitter.

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