Map credit: Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL.

Alaskan Way Viaduct, Washington

Status: Completed
Originally reported cost: $3.1 billion to $4.1 billion

Update from Highway Boondoggles 5, 2019: Traffic “disappeared,” revealing an expensive new highway as unnecessary

After a 2001 earthquake damaged the Alaskan Way Viaduct, an elevated highway along Seattle’s downtown waterfront, the city began planning a replacement tunnel that would increase total traffic capacity. In 2014, we wrote that the tunnel project not only came with an exorbitant price tag, but it was also unlikely to reduce congestion according to the state’s own data. Rather, the city could create more cost-effective and sustainable transportation with a “streets-and-transit hybrid alternative, a combination of a four-lane urban-scaled street on the waterfront, one additional lane on a nearby interstate highway, and hundreds of millions of dollars in improvements to city streets and area bus service.”

Nevertheless, Seattle moved forward with the tunnel. After falling more than three years behind schedule and running more than $200 million over budget, the tunnel opened in February 2019. But before the tunnel opened, the closure of the old Viaduct highway provided a “real-time experiment” of what happens when a city removes an urban highway, as Streetsblog wrote. The Viaduct was closed three weeks before the new tunnel was set to open, an event termed “Viadoom” by the local media, with predictions of interminable traffic jams in the period between the closing of the old highway and the opening of the new. But the predicted traffic never appeared.

Instead, with both highways closed, the traffic seemed to melt away. The Seattle Times asked: “What happened to the 90,000 cars a day the viaduct carried before it closed?” There wasn’t just one answer. More people commuted by bus, bike and water taxi, with transit riders benefitting from expanded service made possible by a recent boost in local public transportation investment. Others changed their commutes or just worked from home. The phenomenon was induced demand in reverse: Remove highway capacity, and people find ways to drive less. As Mark Burfeind of INRIX, a traffic analytics company, told the Times: “For lack of a better term, the cars just disappeared.”

Today, the new tunnel is up and running. Many commuters have resumed their old habits, and peak time traffic counts are already slightly higher than they were on the viaduct. With the project finished, Seattle is now facing a future of more cars and traffic. But Seattle’s experience of removing an urban highway – and watching traffic just disappear – should serve as a lesson for future projects in the area.

Update from Highway Boondoggles 4, 2018:

The Alaskan Way Viaduct replacement project includes the construction of a two-mile tunnel to bypass downtown Seattle, a mile-long stretch of new highway to connect to the tunnel, a new overpass to bypass train blockages near Seattle’s busiest port terminal, demolition of the viaduct’s downtown waterfront section, and a new Alaskan Way boulevard along the waterfront. The purpose of this massive project is to replace the existing Alaskan Way Viaduct, an elevated section of State Route 99 that is aging and vulnerable to damage from earthquakes.

The project, a $3.1 billion undertaking, was mired in controversy and delays from the start. “Bertha,” the boring machine being used for the project, was stuck underground for two years after only advancing one-ninth of the way to its final destination, costing the project at least $60 million. Bertha was eventually fixed and completed tunneling for the project in April 2017. The tunnel is set to open to the public in late 2018.

Original story from Highway Boondoggles, 2014:

Seattle’s aging Alaskan Way Viaduct is a crumbling and seismically vulnerable elevated highway along the city’s downtown waterfront. After an earthquake damaged the structure in 2001, state engineers decided that the highway needed to come down, but the question of how (and whether) to replace it sparked nearly a decade of heated debate. The Washington State Department of Transportation (WSDOT) rejected calls to replace the Viaduct with a combination of surface street and transit improvements, choosing instead an option that would result in more capacity: boring a mammoth tunnel underneath the city’s urban core. At 57 feet in diameter, it would be the widest bored tunnel ever attempted, with the full project carrying an estimated cost of at least $3.1 billion and perhaps as much as $4.1 billion.

Digging a double-decker tunnel was always the riskiest option for replacing the Viaduct. Beyond its exorbitant cost, the tunnel carried a high risk of going over budget. In 2010, WSDOT acknowledged a 40 percent chance of a cost overrun, with a five percent risk that overruns could top $415 million. Shortfalls from tunnel tolls represent an additional financial risk: Soon after settling on the tunnel, the state cut its tolling revenue projections in half. State officials later suggested that further reductions in estimated revenue might be forthcoming. Together with other potential revenue shortfalls, some estimates projected that the funding gap could reach $700 million.

Since 2010, the financial risks of the project have only increased. “Bertha,” the “world’s largest tunneling machine,” has been stuck underground since December 2013 and is not expected to be able to resume work until March 2015—and then only if precarious on-site repairs can be successfully completed. The project is also stuck in disputes over whether taxpayers or the project’s contractor must pay the estimated $125 million to repair the giant boring machine to get it going again, and in a lawsuit about whether the rescue operation should even be undertaken.

The expensive tunnel is not projected to improve traffic significantly compared with the rejected streets-and-transit hybrid alternative, a combination of a four-lane urban-scaled street on the waterfront, one additional lane on a nearby interstate highway, and hundreds of millions of dollars in improvements to city streets and area bus service.

WSDOT’s own statistics show that the tunnel, if completed, would likely increase traffic delays downtown compared with the rejected streets-and-transit plan. At best, the tunnel was projected to reduce traffic delays in the surrounding four-county region by only about 1 percent, compared with the rejected alternative; and those delays could have been further reduced by expanding transit service under the hybrid plan.

With the tunnel now stymied, some elements of the hybrid plan have been temporarily put into place to relieve congestion caused by the construction, and have even been extended to accommodate the construction delays. (Their ability to help is, however, hampered by the fact that other transit services in the community are on the chopping block.) According to WSDOT’s 2013 Annual Traffic Report data, traffic at one end of the Alaskan Way Viaduct was on a decline before tunnel construction began, and has since declined even more. In the region, average daily traffic has dropped 23 percent, and transit ridership has leapt 42 percent.

If the tunnel is ever finished, and if a proposal to charge tolls on the tunnel goes through, the project will have spent billions of taxpayer dollars to attract fewer drivers than are using the existing roadways right now. Traffic projections for even the cheapest tolls are at least 8 percent and perhaps as much as 35 percent below what the traffic volume has become during construction.

While the money spent on the tunneling project thus far may never be recouped, state officials have an opportunity to revisit the scope of the project and select options that are less likely to cause financial and traffic turmoil.