It's probably bad juju to talk about things plummeting and the Alaskan Way Viaduct in the same breath, considering that the double-decker, mid-century freeway is considered a collapsing, lethal liability in an earthquake. The state even released this seismic simulation video in 2009 to impress just how dangerous it was to keep the viaduct standing:

But most of our city council and local state lawmakers voted to KEEP THE DEADLY THING PROPPED UP FOUR YEARS LONGER THAN IT WAS SUPPOSED TO STAND—while they build a tunnel under downtown—thereby increasing the risk of catastrophe. But since construction began, traffic is indeed plummeting on the viaduct:

Why's this matter? The deep-bore tunnel under downtown is ostensibly a replacement for the Alaskan Way Viaduct. But truth be told, it's always been an inefficient substitute, even according to the figures of its biggest boosters: The state's data show about two-thirds of the vehicles that had used the viaduct won't use tunnel. As a result, downtown traffic and I-5 traffic will be essentially identical if we don't build the tunnel. But here we are building a tunnel—except right now the project is delayed, at least for several months, because the tunnel-digging machine is broken.

It's increasingly realistic that if we wait for this tunnel to be finished, the viaduct will stay up longer, exposing more people to risk. Which leads the analysts at the Sightline Institute to ask an important question: Do we need this tunnel?

One metric may be traffic on the viaduct, which Sightline points out has already dropped 40 percent due to diversion to transit, diversion to other roads, declining car use, etc.:

There was no fanfare, no outcry from the business community or residents about lost capacity on the Viaduct choking the life out of the city.... At this point, nobody knows if Bertha will ever get moving again, let alone complete her job. But given these figures, maybe it doesn’t matter. Seattle has seamlessly adapted to losing the first 48,000 trips on the Viaduct. No one even noticed. No one even noticed that 40 percent of the Viaduct’s traffic just disappeared! Could accommodating the loss of another 62,000 be that hard if we, I don’t know, tried even a little?

Seattle can survive, and even thrive, without a viaduct or a tunnel.

Cue every West Seattle resident who says the roads are crowded at rush hour and we can't live without a tunnel. And I'll just point out that, again, the state's data show traffic after building the tunnel will be virtually identical to shutting down the viaduct and doing nothing.

So just tear the viaduct now—while the tunnel is being built, bear with the moderate hardship in the meanwhile—so we don't risk turning that simulation into a documentary.