The path is part of a series of projects on Highway 520 and will allow people to take a 2.75-mile walk or bike ride between Medina and Seattle for the first time.

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A new, 14-foot-wide path for walking and biking on Highway 520’s floating bridge is on track to open in coming weeks, transportation officials say, providing a first-of-its-kind connection between Seattle and the Eastside.

But an exact opening date for the trail — which will help link a network of paths on both sides of Lake Washington — remains unknown.

Here we lay out the project’s timeline and scope, after Royce Christensen, of Seattle’s Lake City neighborhood, poked Traffic Lab for an update.

“The commuting possibilities would increase dramatically when opened,” he wrote.

Traffic Lab is a Seattle Times project that digs into the region’s thorny transportation issues, spotlights promising approaches to easing gridlock, and helps readers find the best ways to get around. It is funded with the help of community sponsors Alaska Airlines, CenturyLink, Kemper Development Co., PEMCO Mutual Insurance Company, Sabey Corp., Seattle Children’s hospital and Ste. Michelle Wine Estates. Seattle Times editors and reporters operate independently of our funders and maintain editorial control over Traffic Lab content.

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The Washington State Department of Transportation (WSDOT) for months has said crews will wrap up construction and grant people access to the path sometime this fall.

According to agency spokesman Steve Peer, that remains the case — the calendar season lasts until Dec. 21, he pointed out.

“We’re aiming to make that mark,” Peer said. “It’s not 100 percent sure, but we’re certainly trying.”

WSDOT will release a firm opening date on Dec. 1, Peer said. The timeline could spill into January.

The opening will extend an existing path north of the bridge’s westbound lanes that stretches about halfway across the lake from the Medina side. Seattle’s Montlake neighborhood, about 8,000 feet away, is unreachable but within view. That “out and back” portion opened last summer.

Crews are doing finishing touches on the remaining portion, Peer said, installing light fixtures and a handrail as well as making sure resting stops are adequately equipped with benches and signs. Work under the bridge also is keeping the last section closed for now.

The trail is part of a $4.6 billion series of projects on Highway 520 between Interstate 405 and Interstate 5.

Officials opened the new, six-lane floating bridge to westbound traffic last spring, capping decades of planning and debate over replacing the original structure built in 1963. It is the world’s longest floating bridge.

The replacement effort began as a push to solve traffic woes but grew into a safety mission to modernize the bridge columns, decks and pontoons in case of an earthquake or severe windstorm.

Among the improvements: The new road deck is 20 feet above the water, instead of 13 feet, and it stands on columns over the primary pontoons.

A crowd of thousands packed the new floating bridge on April 2, 2016, for an opening celebration.

But work on Highway 520 is far from over.

Westbound bridge traffic just shifted onto a new deck over Foster Island, a major milestone in helping smooth traffic flow in Seattle’s Montlake neighborhood.

Eastbound motorists are using lanes on the old bridge, and will continue doing so for about a year until crews start a new round of construction: “The Montlake Phase.”

It will include a new Montlake interchange, highway lid and land bridge — construction lasting until 2022 or 2023, according to the agency.

Eastbound and westbound traffic will share space on the new bridge, two lanes in each direction, during parts of that construction.

The work, WSDOT touts, will help connect Highway 520’s walking and biking path on the floating bridge to Seattle’s Washington Park Arboretum, the University of Washington, Capitol Hill and beyond.

The section opening soon already will be greatly improving access to Seattle’s Burke-Gilman and Bill Dawson trails and to Medina’s Points Loop.

“It’s the final piece of the puzzle,” Peer said.

Judging by foot and bike traffic on Interstate 90’s floating bridge, WSDOT expects an average of about 1,000 people per day to use the new path, with fluctuations depending on the weather, he said.

Avid cyclists, dog walkers and Eastside-Seattle commuters have been anxiously awaiting its opening.

Tom Fucoloro, who tracks local biking issues on Seattle Bike Blog, said in a June post “a trail over the 520 Bridge will revolutionize biking in the region.”

“Biking (travel time) from UW to downtown Kirkland, for example, will be cut in half,” he wrote.

A few people are sharing how they will use the path, as part of a media campaign by WSDOT, called #HumansOf520.

A Seattle Public Schools teacher, Christensen said the trail for him will make recreational bike rides on Friday afternoons easier, as well as open the door to teaching possibilities on the Eastside.

“If I got a job over there, I wouldn’t mind that kind of commute,” he said.

And as for the December or January opening date?

At least that could make for a good ride during winter break, Christensen said.

Got a question or suggestion?

Last week, we spotlighted momentum among transit leaders to diversify Puget Sound ferry service. The week before, we explained why road crews choose asphalt over concrete for road-resurfacing projects.

If you have a question or idea for us, send it to trafficlab@seattletimes.com. We may feature it in an upcoming column.