After exploding onto the scene in 2013, Citi Bike's annual membership has declined for the second straight year, according to the Mayor's Management Report. (The report for fiscal year 2015, which ended June 30, was released Thursday.) Last year, the number of trips taken by both annual and daily riders also declined. The report says bicyclists were reacting to a 50 percent increase in membership fees — and the brutal winter.

But Citi Bike says it's on an upswing. The private company that runs the operation has improved its software, docking stations, and the bikes themselves. Meanwhile, it is expanding into new neighborhoods. And this month, Citi Bike broke its daily ridership record three times. It hit a new high-water mark Wednesday, when the system clocked 50,000 rides.

"That shows how enthusiastically New Yorkers are embracing the program, especially as it expands and the weather gets a little nicer, " said John Frost, who directs the bike share program at the New York City Department of Transportation. He predicts Wednesday's record won't stand for long. "I wouldn't be surprised at all," he said, "if we break that a couple more times on some really nice-weather weekdays."