The effort goes well beyond the bridge, though — by about 46 miles.

The activists are campaigning for what they call the Harbor Ring, a roughly 50-mile route that circumnavigates the waterfronts of three boroughs and New Jersey. Starting in Staten Island, it crosses the Bayonne Bridge, heads up the New Jersey Gold Coast to Weehawken, onto a ferry to West 39th Street in Manhattan, down the Hudson River Greenway and the Battery, over the Manhattan Bridge, and finishes on the waterfront in Brooklyn from Red Hook to Bay Ridge.

With booming bike use on both sides of both rivers, the only missing link is the Verrazano.

Not that the Harbor Ring is strictly about transportation.

“We think of this as a matter of infrastructure, one that can promote tourism across the city,” said David Wenger, a lawyer who bikes by the bridge every morning on his way from Brighton Beach to work in Midtown Manhattan. He and Mr. Gertner are board members of the Harbor Ring Committee, which is holding a rally on Saturday.

There is added urgency to their push. Last November, the transportation authority began a feasibility study, which covers new approach roads and ramps in Brooklyn, as well as other structural issues in addition to the bike path. The study will not be completed until 2016, but transit advocates have already expressed concern that there have been no public hearings on the plans.