SEATTLE — A state study suggests that even a modest toll would result in traffic diverting away from a tunnel on the Seattle waterfront onto city streets.
But the state could meet the $200 million it is expecting to contribute from tolling to the $3.2 billion replacement project for the aging, earthquake-vulnerable viaduct. The tolls would also pay for maintenance and interest on the bonds the state needs for the $200 million.
The state Department of Transportation study was presented Wednesday to the Advisory Committee on Tolling and Traffic Management — a joint government committee studying how to raise the $200 million.
The study looked at tolling ranges between 75 cents to $3.25 to meet the $200 million needed.
It found that “even modest mid-day tolls” led to diversion of between 30 and 50 percent of the expected traffic on the tunnel. It suggests that drivers taking long trips would pay for a toll, but in-city drivers would opt for city streets.
The viaduct typically carries 110,000 vehicles a day.
One scenario that achieved the $200 million needed had tolls between $1 and $3.25, depending on the time of day. The second scenario had a range of 75 cents to $2.50 but those rates would be increased in 2030. One scenario in which tolls were set between 75 cents and $2.25, but saw no increase in 2030 would not raise enough money.
The findings of this study echo the results of a study released last June. That study suggested that an extra 9,100 cars could spill onto surface streets during the afternoon commute in 2017 if tolls were $3.50 southbound and $2.50 northbound. That’s about 42 percent of traffic that would use an un-tolled tunnel. At the time, project administrator Linea Laird said this that no other money is currently available to the state Department of Transportation.
With these two studies completed, the committee will present another set of scenarios by spring, said Amy Grotefendt, a DOT spokeswoman.
The committee will think of ways to “discourage people from diverting from the tunnel,” Grotefendt said.
The early stages of replacing the Alaskan Way Viaduct with a tunnel have already begun with crews tearing down the southern section of the elevated highway. The Department of Transportation projects the finished, four-lane tunnel is expected to open at the end of 2015.