The express toll lanes are moving more cars per hour than their HOV predecessors.

But that’s not true for every spot along the way, particularly the one-lane section of the northbound lanes in Snohomish County, according to a Street Smarts look at state data.

Here, traffic volumes in the former HOV lanes have stayed unchanged or gone down northbound. And what bright spots there are going south are well short of dramatic.

The challenge northbound is most pronounced at the end of the lanes — near the junction with I-5 — where the former HOV lane used to move 11 percent of all northbound vehicles. That share slipped to 9 percent a year later in December 2015.

The state aims to help the north end in both the coming weeks and the coming years.

In the short-term, crews will move back double-white striping by about 400 feet to give drivers more room to merge to I-5 — offering an incentive to stay in the lanes until they end rather than bail early to aid a slow-moving crawl across multiple lanes of heavy traffic.

In the long-term, the state plans to use toll revenue to add a second toll lane in the northern half, both northbound and southbound, eliminating a bottleneck it created when it added a second toll lane at Kingsgate. Transportation officials also plan a direct access connection to Highway 522 with a new interchange. Together, the projects total an estimated $570 million.

There’s no timeline for the work. Expanding tolling to Renton for a 40-mile network is the next step, and that likely won’t be completed until 2022 at the earliest.

The state continues to tweak striping and stenciling to address concerns in other spots along the Lynnwood-to-Bellevue corridor.

“We’ll continue to monitor access points and listen to driver feedback to identify challenging areas,” said Ethan Bergerson, a spokesman for the Washington State Department of Transportation.

It is early in the project. State officials have said it will take six months to a year for tolling patterns to settle in on I-405. They are aware of problems in the north end, but remain committed to seeing tolling through its first two years before making any dramatic changes.

With about 4 in 10 express toll lane users coming from Snohomish County, though, relief can’t come soon enough.

A second express toll lane is the kind of added capacity that has brought more dramatic improvements in the southern half of the project, which follows national trends.

South of Bothell, vehicle-counting checkpoints have logged as much as 62 percent more vehicles in the two express toll lanes than were in the single HOV lane the previous year.

At its most dramatic, the two southbound express toll lanes in Kirkland approaching NE 85th Street were carrying nearly 1 in 4 of all southbound vehicles last month. That’s a leap from the 15 percent share the single HOV lane had last year.

With the number of general purpose lanes remaining the same, that spells relief for those choosing the “free” lanes. In the north end, general purpose lane volumes have not changed significantly.

That translates to differences in speed, too.

At the height of the morning rush hour in December, drivers in the double-express toll lane section south of NE 160th Street were going nearly 58 mph — compared to 34 mph in the single toll lane coming out of Snohomish County.

Speeds in the general purpose lanes also reflect the difference, though it remains slow-going no matter where you are. Average general-purpose lane speeds in the southern half came in at 29 mph, compared to about 16 mph in the north end. There are more general purpose lanes in the southern half, too.

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