The triple cantilever runs along the edge of Brooklyn Heights, a wealthy and politically connected neighborhood. It stands as a symbol of resistance to Robert Moses, the power broker who rammed highways through communities.When Mr. Moses tried that approach here in the 1940s, Brooklyn Heights residents pushed back, and Mr. Moses rerouted the Brooklyn-Queens Expressway around them.At the top sits the Brooklyn Heights Promenade, a cherished landmark with skyline views where generations of New Yorkers have come for their first date.Below, two levels of traffic jut out like drawers pulled from a dresser. The highway is the main artery between Brooklyn and Queens, and it is part of Interstate 278, the only road that connects New York’s five boroughs.The cantilever, which opened in 1954, was designed to be used for 50 years. The risks only go up as it continues to deteriorate year after year, even as its life span has been extended with interim measures. While city officials and transportation engineers say imminent collapse is not a threat, other catastrophes could still strike, like concrete falling off and hitting vehicles.Since 2018, two New York City mayors — Bill de Blasio and Eric Adams — have announced that they would fix this vital artery. But both administrations were unprepared for the ferocious community opposition to their ideas on how to proceed. Both struggled to build any consensus at all as local residents countered with their own ideas. The endless back and forth led to more delays and inertia. Traffic on the triple cantilever passes through Brooklyn Heights. Erin Schaff/The New York TimesThe standoff over the B.Q.E. has become, more broadly, a symbol of the power that local communities wield over critical infrastructure projects around the nation.Though community opposition is hardly new, it is thriving today as residents have become more nimble and sophisticated at influencing projects, or halting them entirely. They strategize about just who to target