By Ethan Bergerson
A lot has changed in the Puget Sound region since the I-405 express toll lanes opened in 2015. With a new driver moving to the area every six minutes, the population boom poses a huge challenge to all of our roads. Before the express toll lanes opened, there was no way out of traffic on I-405 but now people have a choice for a faster trip when they need it. While I-405 still experiences daily congestion, the express toll lanes are providing a more dependable option than the old HOV lanes could and even people in the regular lanes are moving faster in most areas than they were two years ago, despite there being more vehicles on the road than ever before.
I-405 is moving more people than ever before
The population boom means more vehicles are using every major Puget Sound highway, and none has seen as rapid a growth as I-405 between Bellevue and Bothell. Traffic volumes in this area have increased twice as fast as on I-5 through Seattle, and this section of I-405 is carrying 10 percent more vehicles a day than it did two years ago.
But even with more people, this portion of I-405 is now moving as fast or faster across all lanes than it was two years ago.
How's this possible? We've made dozens of improvements to I-405 since 2015, and we're getting extra mileage out of them because express toll lanes are more efficient than regular lanes when traffic is at its worst. At the height of the peak commute, each express toll lane is carrying 20-30 percent more vehicles than a regular lane in some places, which helps the entire highway flow more smoothly. And when drivers choose to leave the regular lanes to use the express toll lanes instead, they free up space for the other drivers around them. That all means that we're getting a lot more benefit from the new lanes we built in 2015 than if that space had been used for regular lanes instead.
Express toll lanes are working well in many ways
For most parts of I-405, there is no question that the express toll lanes are working a lot better than the old HOV lanes which came before them.
Every day, more than 60,000 drivers choose to use the express toll lanes for a faster trip. About two-thirds of those people are choosing to pay a toll, and a third are riding in the lanes for free in a carpool, motorcycle, or bus.
surveyed I-405 drivers this summer, about two-thirds of people agreed that they liked the option to use the express toll lanes and believed they reduce congestion for some trips in the regular lanes.
During peak commute times, the average toll is about $3, which typically saves drivers 10-15 minutes (or more when tolls are higher). On average, the express toll lanes move 19 mph faster than the regular lanes going southbound in the mornings, and 23 mph faster than the regular lanes heading northbound in the evenings.
How do we measure success?
One way that we measure success is to look at the percentage of time during peak periods when the express toll lanes are able to move at 45 mph or faster. That's roughly the speed when the system is flowing most smoothly and carrying the greatest number of vehicles at a time. When the express toll lanes opened, the state legislature set a goal that they would move at this speed 90 percent of the time.
give drivers more space to merge, improve access points, and build a new peak-use shoulder lane.
But the southbound morning commute from Lynnwood to Bothell is still a big challenge. This area only moves at 45 mph about 63 percent of the time. Moreover, this challenging section brings the overall average for the entire system down to 85 percent, just short of the 90 percent goal. The old HOV lanes only met this standard 56 percent of the time in 2015, so this is a still an improvement compared to two years ago despite all the new cars on the road.
What does this mean for future travel on I-405?
When the express toll lanes were authorized, the Legislature provided two metrics by which to measure the lanes' success during the first two years of operation: that the lanes pay for themselves, and that traffic moves at 45 mph 90 percent of the time during peak travel times. The lanes are meeting the first measure easily, and are coming close to the second. Now that the lanes have been operating for two full years, we're working with legislators to determine the next steps for the express toll lanes.