ThunderTunnel! 1.3 Cars Enter, 1 Car Skips the Toll

Illustration courtesy WSDOT

“The average person might be surprised at how much roadway is proposed to supplement the tunnel,” goes Mike Lindblom’s story in the Seattle Times. But not you, the SunBreak reader, because it has always made me crazy when people argue that the tunnel’s burial of SR-99 would keep cars from “choking up” the waterfront.

In a perfect world — of someone’s imagining — the waterfront might be a wildflower-lined deer track, but that’s never been on the table. The waterfront is already served by a multi-lane roadway for the simple reason that it’s a busy area serving tourists, travelers (cruise, Clipper, and ferry), and freight, as well as Seattle residents, many of whom are already avoiding the Viaduct.

Given the tunnel’s bypass of Seattle’s downtown, the limits on the size and kind of freight that can use the tunnel, and the necessity of tolling to pay for the tunnel’s expense, the ugly truth is, as Lindblom spells out, that projections call for the tunnel to handle 47,000 trips per day when it opens, and the waterfront boulevard to take on 35,000.* (NB: The costs for a deep-bore tunnel and a boulevard don’t split along the same lines.)

From the ferry terminal south to SoDo, the boulevard would have six lanes; to the north, four; and traffic would tootle along at 30 mph.

It’s counterintuitive, but in congested situations, 30 mph is faster than a limit of 50, because attempts at lane changes, exits, and entries at 50 during rush hour can easily bring everything to halt. (Of course, over one or two miles, even if you could drive at top speed, you’re not saving any real time compared to 30 mph. It’s a question of seconds.)

So there you have it — the tunnel’s lack of access to downtown plus the each-way toll (which the state will need every penny possible of to help cover the funding gap) combine to push almost half the Viaduct’s traffic to the waterfront. In fairness, I have to admit that tunnel tolling also leaves the door wide open for congestion-tolling in the Seattle core, the same way that SR 520 tolling implicates I-90.

*The math-conscious among you will note this only adds up to 82,000, less than the 110,000 the Viaduct is supposed to handle. I think the remainder can be attributed to diversions to I-5 and discretionary trips that simply vanish as people think better of fighting traffic.