In downtown Los Angeles, the population and night life have exploded in recent years, in part because it is the easiest area to get around without a car. A bike-sharing program, clustered around public transit stops, is coming to the neighborhood next year, with plans to expand around the city from there.

Mike Bonin, one of the city councilors who sponsored the mobility plan, said residents were eager to go “car-light.”

“The number of folks who say they’d like to bike or walk more is huge,” Mr. Bonin said. “And the number who say they don’t because they think it’s not safe or clean or convenient is roughly the same.”

But the car still reigns: Nearly 80 percent of Los Angeles commuters get to work by car, with most of the rest on buses and only 1 percent on bikes.

Bruce Feldman, who has lived in Southern California for more than six decades, worried that under the transportation plan, residents could end up fenced into their own neighborhoods by traffic. The number of intersections where traffic crawls most slowly, according to city estimates, will double by 2035 under the plan.

“There are so many things going on in L.A., but if you can’t get to them, what’s the point of living here?” said Mr. Feldman, 67, who runs a luxury gift business and lives in Santa Monica, which already has its own network of bike lanes — and gridlock problems. “I’m not opposed to bikes, but you’re going to be dead before you see the city these people envision, so what do we do until then?”

Though the plan passed the City Council in August with overwhelming support, obstacles remain. In addition to the lawsuit, local opposition could become stronger once city transportation workers are preparing to paint over lanes.