Most motorists who drive Highway 520 would keep crossing Lake Washington there, even if faced with a round-trip toll as high as $6.85 on a new bridge, according to a state study released Wednesday.

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Most motorists who drive Highway 520 would keep crossing Lake Washington there, even if faced with a round-trip toll as high as $6.85 on a new bridge, according to a state study released Wednesday.

The study was designed to gauge what toll levels are realistic, how drivers might react to them and how much money could be raised to pay for a six-lane replacement bridge. Gov. Christine Gregoire and the Legislature say they’ll make decisions on a bridge design and tolls next year.

The study lays out four scenarios. Two would toll only the 520 bridge — one starting in 2010 and one in 2016 when the replacement is competed.

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The two others also include tolling on the Interstate 90 bridge at the same rate in 2016. Those were far more lucrative, each raising more than $2 billion for construction, compared with $900 million or less for the 520-only options.

Even in the face of one-way peak-commute tolls ranging from $2.15 to $3.80 — that’s in today’s dollars and will rise with inflation — the study says most people would pay to cross the 520 floating bridge rather than stay closer to home or find other routes.

“The majority of the people stay on the bridge and pay the toll,” said Charlie Howard, a senior planner for the Puget Sound Regional Council, which published the study along with the state Department of Transportation.

But about half of more than 150 respondents in an online Seattle Times reader forum Wednesday afternoon wrote otherwise.

“It will keep me from ever using that bridge,” one reader wrote. “I hope the good people of Kenmore and Renton like me jamming their roadways.”

Others worried that drivers who now cross Lake Washington on the bridge would jam other highways as they sought non-tolled routes. One predicted most drivers would find other routes “just out of principle.”

“Good for everyone”?

If tolls for 520 begin in 2016, about 16 percent of drivers would avoid crossing the lake, in part because people would have time to change their housing or work locations, the study says. Another 6 percent would take a different route.

Lower toll rates of 75 cents to $1.50 each way would be charged on weekends. Some options assume tolls of 40 cents to 80 cents for partial trips, such as from I-5 to the Montlake exit, or from I-405 to shoreline towns on the Eastside. On I-90, Mercer Islanders would pay a half-toll to enter Seattle, or a half-toll heading to Bellevue.

Oddly, the report predicts only 3 percent of 520 bridge motorists would switch to transit or car pools, even though a new high-occupancy-vehicle lane and more buses would exist by 2016. “I think it’s going to be higher,” Howard said, acknowledging that more research needs to be done.

One Times forum respondent wrote about the tolls: “It would encourage me to bus. So, this could be good for everyone.”

About 115,000 motorists per weekday cross the existing four-lane bridge.

Tolls would keep enough people off the bridge that trips would become faster for those who pay, the study says.

Average afternoon speeds of 26 mph would improve to 40 mph if the existing bridge is tolled in 2010, the study says.

Under all scenarios, some drivers would detour to Highway 522, around the north end of the lake, but not in large-enough numbers to create huge slowdowns, the study predicts. The I-90 bridge — even untolled — has the capacity to handle any increased traffic the 520 toll might create with a modest reduction in travel speeds, it says.

I-90: a sensitive subject

The study will be used by a 520 Tolling Implementation Committee, which will report back to Gregoire and the Legislature next year. Its members emphasized that Wednesday’s numbers are merely a starting point for discussions. The committee doesn’t plan to recommend a particular option.

“We could look at a blend — where you have a lower toll from 2010 to 2016, and a higher toll after 2016,” for instance, said Transportation Commission member Richard Ford. Other committee members include state transportation Secretary Paula Hammond and Bob Drewel, executive director of the regional council.

And there are still related issues that must be dealt with.

The state has yet to make a design decision for the difficult Montlake interchange.

Tim Eyman’s Initiative 985, which has qualified for the November ballot, seeks to block any I-90 tolls from being used toward Highway 520.

State lawmakers have been reluctant to suggest tolling I-90, because of an expected public backlash. But state Treasurer Mike Murphy said tolls are needed on both bridges to make the finance plan work.

“If there’s tolling on one, there should be tolling on the other, and it should be simultaneous,” he said Wednesday. If not, he said, lawmakers would have to add huge amounts of other tax money to the 520 project.

None of the Highway 520-only toll plans fills the current funding gap, which is $1.5 billion to $2 billion, for the $3.9 billion construction project across Lake Washington.

The bridge was built in 1963, and studies about expanding bridge capacity began in the 1980s. Engineers say it could be destroyed in an earthquake or severe windstorm.

Mike Lindblom: 206-515-5631 or

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