NEWPORT, R.I. — A bike path running the length of Aquidneck Island reached another milestone recently, representing a rare show of collaboration between communities on civic projects.

The latest phase of the 18-mile Aquidneck Island Bikeway, costing between $2 million and $4 million, is expected to benefit recreational bikers as well as commuters. The bike lane heads from Easton’s Beach, along the western edge of Aquidneck Island, to the new Sakonnet Bridge bike lane in Portsmouth. A bike path is planned for Tiverton. The bikeway also connects with the Mt. Hope Bridge, although bike travel over the bridge, which connects to Bristol and eventually the East Bay Bike Path, is perilous.

At a July 15 ceremony near Naval Station Newport, the project was hailed as a collaboration between local, state and federal agencies, as well as serving as a rare show of cooperation between neighboring cities and towns.

“What else can we do to link our cities and towns?” Mayor Harry Winthrop asked.

Representatives from Middletown and Portsmouth also noted that the bike path will benefit the local economy and tourism, while easing traffic congestion. Sharing schools and other municipal services were also suggested.

Bicycler Bob Gessler of Portsmouth recalled when roads had too many potholes for biking. “I’m glad to see the bike path is happening,” he said. “It’s got a lot of great potential.”

The Aquidneck Island Planning Commission is overseeing the bikeway project. The $75,000 design study was funded by the van Beuren Charitable Foundation and is expected to take a year to complete. The remainder of the funding will likely come from federal transportation dollars.

The original concept was conceived through a multi-model transportation study completed in 2011. So far, the state Department of Transportation (DOT) has spent $216,000 for planning and striping of bike lanes on Coddington Highway and Memorial Boulevard.

About a third of the bikeway is complete, and most of the lanes will share existing vehicle roadways. A portion of the path will eventually be created to avoid a congested portion of West Main Road in Middletown. The larger $25 million “rail and trail” segment of the Aquidneck Island Bikeway is expected to be completed in 10 years. The master project includes a rebuilt pier on the western edge of the island for picnics, water access and a boat landing.

Tina Dolen, executive director of the Aquidneck Island Planning Commission, said a destination known for boating is now a pioneer for biking and regional planning. “The bike path will be an anchor for Aquidneck Island,” she said.

In addition to the environmental and health benefits, Dolen said the bikeway also helps low-income residents and workers travel and gain access to walkable areas and public transit.