Good news for travelers on northbound Interstate 405 in the south Snohomish County area: In less than a week, you’ll have a new option for your afternoon commute.
At 2 p.m. Monday, April 24, the I-405 northbound peak-use shoulder lane will officially open to general-purpose traffic on the 1.8 mile stretch between State Route 527 and I-5. Between now and then, we’re wrapping up our testing of the new electronic signs that will control the lanes, so you might still see some test messages, symbols and colors as you drive through the area.
A green arrow like this will indicate if the new I-405 peak-use shoulder lane is open to traffic.
Originally, the Washington state Legislature funded this project with an expected opening date in 2018. However, with approval to use revenues from the I-405 express toll lanes earlier, we were able to complete the project more than a year sooner than expected.
How do I use the lane?
As the name suggests, general-purpose traffic and buses will now be able use the northbound right shoulder as an additional lane during times with the heaviest congestion—in this case, the weekday afternoon commute. That means there will effectively be three regular lanes and one express toll lane in this area.
The peak-use shoulder lane will generally be open during the afternoon peak period but will be dynamically controlled, so be sure to check the overhead electronic signs before entering the lane.
A green arrow will indicate that the lane is open, and a red “X” will indicate that the lane is closed, similar to the signs you see today on I-5 near downtown Seattle.
During off-peak hours and weekends, the shoulder will remain closed so that crews still have space to perform maintenance, and law enforcement and emergency services can use the shoulder as needed.
As with all highway operations, our traffic management center will be actively monitoring the shoulder lane. If there is a collision or incident, we will be able to close the lane in order to allow emergency services to respond. There will also be four paved emergency pullouts in the area of the peak-use shoulder lane.
Although this is the first electronically controlled shoulder lane of its kind in the area, you may have noticed that US 2 in Snohomish County also allows traffic on the shoulder during specific hours indicated on posted signs. For more information on other peak-use shoulder lanes in the region, check out the WSDOT congestion page.
Why did we add a lane in this area?
There have always been northbound bottlenecks at the SR 522 and SR 527 interchanges because we simply don’t have enough lane capacity to handle the huge growth that south Snohomish County has been experiencing.
At the SR 527 interchange, an estimated 1,000 vehicles an hour enter northbound I-405 during the afternoon commute. For perspective, that’s more than two full Kirkland Costco parking lots emptying on to northbound I-405 from SR 527 every hour. The peak-use shoulder lane will offer a new place for some of those vehicles to go without needing to merge directly into the already crowded I-405 lanes.
After we opened the dual express toll lane in September 2015 between downtown Bellevue and SR 522, we found that traffic is flowing more smoothly through Kirkland, where we have five total lanes. But north of SR 522, where we did not add any new capacity and have only three lanes, we’re still seeing heavy traffic.
As a result, most trips between Bothell and Lynnwood on northbound I-405 are now slower during the afternoon commute than they were before express toll lanes. The peak-use shoulder lane is just one of several identified improvements that we have been able to make over the past year and a half based on driver feedback.
We’ll be closely monitoring how the peak-use shoulder lane affects traffic in the coming months, but we know that this area of I-405 still needs more help. That’s why we’re continuing to look at how to fund and build additional improvements between SR 522 and I-5, including extending the second express toll lane farther north and improving the SR 522 and SR 527 interchanges to help traffic move more smoothly.
The Legislature gave us initial funding in the 2016 budget to study these improvements, and the governor’s budget for next year includes $5 million more to continue our engineering.
Especially with Sound Transit planning to launch a new I-405 Bus Rapid Transit system from Lynnwood to Tukwila by 2024, we know it’s critical that we help keep traffic moving and provide travelers with a more reliable trip option.
In short, the peak-use shoulder lane isn’t the end of the road — it’s just the start of what we hope will be a series of big improvements for the north end of I-405.