From Seattle-PI’s Getting There column:

Question: Greg Anderson asks if big trucks should be banned from Interstate 5 express lanes and provided with a new bypass to the freeway to help traffic flow.

“Every day during rush hour, both morning and night, I see semi-trucks in the left lane approaching the entrances to the express lanes,” he said.

“They are of various sizes and haul assorted loads — no doubt some flammable. The immediate effect is the slowing of the traffic in the lane next to the commuter (car pool) lane going south on I-5 and in the lane that is the entrance to the express lanes … . I wonder why the semi-trucks are allowed to use the express lanes at all considering that an accident there might effectively end the use of the express lanes as a whole for the better part of the day.

“Prohibiting the use of the express lanes to truck and tractor traffic would, seemingly, reduce the congestion considerably, in both directions.”

He wonders if “any thought (has) been given to creating a truck bypass lane around the east side of Lake Washington, similar to the one going north through Portland, so that trucks not needing to stop in the Seattle area could use that lane to get through.”

Maybe Greg moved here a short while ago, but I-405 on the Eastside used to do what Greg has proposed. The key phrase there is “used to”. “Originally intended as a bypass to I-5 through Seattle, I-405 has experienced a large increase in traffic volume since its construction. I-405 is now the most congested freeway in Washington State, particularly the segment between State Route 169 and I-90.”

Congestion may be the problem but roads aren’t the answer. If we build more roads, congestion will follow. With the fast growth of the suburbs, any new freeway built will become just as congested as 405 as people move further and further away from the city centers trying to find less congestions, yet still depending on those same urban centers for jobs and entertainment. Easing congestion will require a different frame of mind than most people are willing to adopt, though it’s been shown to work in the not-so-distant past.

The DOT came to the same conclusion. Getting There’s answer to the question posed by Greg:

“Keeping traffic moving is one of WSDOT’s top priorities,” Conrad said, but “adding an additional lane to I-5 for freight traffic would prove to be a very costly venture, and would do little to relieve congestion in the Puget Sound area. Truck traffic is not the reason Puget Sound highways are congested.”