OLYMPIA, Wash. (AP) - Gov. Chris Gregoire on Thursday proposed that motorists pay about half of the $4 billion cost of replacing the aging Evergreen Point Floating Bridge across Lake Washington with tolls beginning next year.

Gregoire said the 44-year-old Highway 520 bridge is aging and is at risk of sinking if an earthquake or major windstorm hit.

Last November, voters in the region rejected a plan that would have paid more than $1 billion to replace the bridge. The state and federal government already are on the hook for about half the replacement cost.

The governor's simple plan, quickly endorsed by political and community leaders, would fill the rest of the financing gap with tolls, with cheaper crossings during off-peak hours.

The new Tacoma Narrows Bridge is being financed with tolls, as was the existing 520 bridge. Olympia leaders have said many new mega-projects will require tolls.

Gregoire's plan doesn't spell out the amount of the tolls, although a recent study suggested between $5 and $10 roundtrip during rush hour, in 2007 dollars, once the bridge opens in about 2018.

One of her more controversial proposals is charging tolls on the old bridge, beginning sometime next year, until the span is torn down. A study recommended about $6 or $7 roundtrip during peak-hour commutes in that case.

Her plan doesn't say whether tolls would be charged on the nearby Interstate 90. Transportation engineers say that many motorists would shift to the I-90 crossing if it were free and the 520 bridge were tolled.

The 520 plan now goes to the Legislature. Earlier this week, at a pre-session forum sponsored by The Associated Press, transportation leaders spoke favorably of toll legislation, both for this project and others around the state, including a new Interstate 5 bridge across the Columbia River at Vancouver.

The Evergreen Point Bridge carries about 160,000 vehicles a day. It was built in the 1960s without today's design standards and is deemed at risk of collapse in a strong earthquake or severe windstorm.

The governor's preferred design is for two general-purpose lanes one high-occupancy vehicle lane in each direction. The span could be widened in the future.

"The bridge is aging, and as any driver knows, it is also slow and crowded," the governor said in remarks released by her office. "The time for action is now. We need to step up and fix this problem for the sake of Washington families and a vibrant economy that depends so much on this vital link."

Gregoire said cheaper tolls during off-peak hours should relieve some of the rush-hour congestion. King County Executive Ron Sims said variable tolling, improved transit and more telecommuting should prompt motorists to change their driving habits and reduce pollution.

"Half the climate pollution in this region comes from cars and trucks," said Seattle Mayor Greg Nickels. "It is the biggest challenge we face in turning the tides on global warming.

"We must find ways to encourage people to think about the trips they take - and to not drive alone. Tolling will better reflect the true costs of driving."

Bellevue Mayor Grant Degginger said the bridge is "on its last legs" and that congestion has grown intolerable.

"The devil will be in the details for both the design and the financing package," he said.

One voice of dissent was the House Republicans' transportation leader, Doug Ericksen, R-Ferndale, who called it "Governor Gregoire's Plan to Nowhere." He said a 2018 target date is unacceptable and that the design is too expensive, while doing too little to relieve congestion.

"It's amazing that we will have to wait until 2018 to address an emergency," he said.