After seven tries, the folks studying Highway 99 tunnel tolls may have untangled a knot — by suggesting a simple rate of $1.25 peak and $1 the rest of the time.
Those amounts are reduced from earlier peak numbers (as high as $3) that threatened to cause intolerable traffic diversion onto downtown Seattle streets, yet they exceed some low-cost scenarios (as cheap as 50 cents midday) that would tear a hole in the tunnel’s budget.
So-called “Scenario 7” hasn’t been approved, but will be discussed further in the next work session, tentatively scheduled for late October, said Maud Daudon, chairwoman of the Advisory Committee on Tolling and Traffic Management, after a meeting Wednesday.
Scenario 7 represents the best balance between generating money and minimizing traffic diversion, said Mark Bandy, traffic engineer for the state Department of Transportation.
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Nonetheless, the DOT predicts 4,200 drivers would still avoid the tunnel during the three hours of peak traffic in the afternoon — enough to aggravate downtown congestion, especially if possible bus-service cuts occur, or if the state and city road departments fail to improve traffic signals and freeway bottlenecks.
Those 4,200 vehicles would be enough to fill two surface-street lanes downtown, plus one lane on First Hill east of Interstate 5, said Bob Chandler, deputy director for special projects at the Seattle Department of Transportation. Downtown has 17 to 19 north-south lanes, and there’s no space to build more, Chandler said.
Also, the city is moving to create protected bicycle lanes and a streetcar, while still maintaining bus lanes. A single collision, crime, protest or festival can trigger gridlock now.
“Our system really is rather fragile,” said Kevin Desmond, general manager for King County Metro Transit.
The agency is pressing for new taxes to avert a service cut next year, when state aid for Highway 99 transit and a King County $20 car-tab fee are both set to expire.
Daudon said a major challenge is to handle the economic boom from Amazon’s growth in South Lake Union and its three-tower campus planned for north of Westlake Center.
Ultimately, it will be the state Transportation Commission that decides the toll amounts. The advisory committee can only issue a recommendation.
Lawmakers have demanded that the tolls pay off $200 million in construction debt for the $3.1 billion replacement for the old Alaskan Way Viaduct, of which the $2 billion tunnel — scheduled to open by the end of 2015 — is the costliest part. Over 30 years, tolls also must cover $160 million in operating costs, a $190 million fund for major repairs, and $55 million to $85 million for insurance — and the estimated $350 million cost to collect the $1.1 billion in toll payments Scenario 7 is expected to generate.
The toll committee changed some assumptions to find a balance. Scenario 7 would charge tolls around the clock, and it assumes annual toll increases of 1.3 percent.
The embrace of seven-day tolling underscores how conditions for Seattle travelers are in flux, even in just four years since the tunnel was chosen. Transit ridership is growing rapidly, and only a third of downtown workers drive solo.
On Saturday afternoons, traditionally regarded as an off-peak time, it’s now common to see stop-and-go traffic on I-5 — so maybe there’s not such a temptation for drivers to use the freeway merely to save $1.
Mike Lindblom: 206-515-5631 or email@example.com