The new SR-99 tunnel has a problem.

No, Bertha isn’t stuck again. This time, problem is financial: setting the toll rates.

The initial results of an investment-grade analysis of tolling options, performed by a consultant for WSDOT, show that setting a price point for the new tunnel continues to be as tricky a proposition as it was for other highways in the region, where new tolls spurred howls of protests from angry drivers and led to worsened traffic on competing routes. Toll rates must find the sweet spot between two competing ideals. They must be high enough to raise the $200 million pledged to construction costs of the $3.2 billion tunnel and viaduct replacement. But they must be low enough that drivers will pay them, rather than veer off onto Interstate 5 or downtown surface streets, both of which are already at or near capacity.

For any price above $0, their will be some diversion to surface streets. The only real solution is to toll the surface streets. All of them.

Congestion pricing – a fee to enter the downtown core – has worked successfully in London, Singapore, and Stockholm. Drivers are charged via a similar tolling system to the one on the SR 520 bridge. Congestion pricing allows buses to move faster and, crucially, provides additional revenue for transit service. Chad Newton wrote a great guest post a couple years back on how it could work.

Seattle City Councilmember Mike O’Brien put $200,000 into this year’s budget to study congestion pricing in Seattle. The Deputy Mayor, Shefali Ranganathan, has spoken positively of the idea.

Some will argue that congestion pricing is regressive. It’s true that it doesn’t scale with income, but it’s important to keep in mind that most of the poorest people arriving downtown during the workday come by transit. Parking costs north of $300/month in downtown garages.

Seattle, with its hourglass shape and water boundaries, is a natural fit for congestion pricing. The city has tried and failed for 15 years to significantly reduce its carbon emissions. The best way to get there is to significantly reduce car traffic. Congestion pricing will help with that goal.