This has been the summer of the bike. Last month, New York City’s new Citi Bike bike-share program set an impressive record: After only about two months in operation it logged its 2 millionth ride. The system is now reportedly averaging about the same as London’s program, Barclays Cycle Hire.

At least half a dozen other U.S. cities are expected to roll out bike-share programs before the end of 2013, and many are likely to be emulating the Citi Bike model. "Sixty percent of percent of the population would like to ride," Gabe Klein, commissioner of the Chicago Department of Transportation told Wyoming Public Media, earlier this year. And programs like Citi Bike — a network of strategically located, automated rental stations that store rental bikes which can be returned at any station in the system — are supported by the National League of Cities’ Sustainable Cities Institute as one part of an overall sustainable transportation strategy.

But if the program isn't designed right, flaws in safety and efficiency could seriously hinder success. That means taking into account hard lessons and unexpected consequences that New York encountered. Here are four things that those planning similar programs can learn from Citi Bike.

Bike-share docks are not just for parking. Citi Bike launched on May 27, and since then residents have found some unique ways to use the bikes and stations. According to The New York Times, bikes parked at the docking posts located around the city have been used as temporary seating, exercise stations, and places for children to play. They’ve also, unfortunately, been used as trash receptacles.

Prepare to avoid technical glitches. On April 15, a system software glitch reportedly exposed the personal information of more than 1,000 account holders. Users were informed of the breech via letter, and a statement from the Department of Transportation claimed, “There is no evidence that any personal information was maliciously accessed or misused.” A number of publications, including The Wall Street Journal, ran stories on the issue.

Bike-share program safety requires innovation. As more people adjust their lifestyles to make the most of traveling by bike, new ideas are popping up to ensure the safety of riders. One such innovation is HelmetHub. This solar-powered helmet vending machine is designed to encourage more bike share riders to wear helmets by making access more convenient. It was created by a group of Massachusetts Institute of Technology students and it rolled out in Boston earlier this year.

 It is possible to have too much of a good thing. Within just a few days of its launch, Deputy Mayor Howard Wolfson tweeted that Citi Bike had already exceeded 20,000 annual memberships. About a month later ABC news reported that “it has become so popular that many bike racks in midtown Manhattan are often empty during week day rush hours.” In response to the demand, New York’s Department of Transportation has updated its plans for expansion. In a decision championed by Sen. Michael Gianaris (D-NY), the transportation department has announced that Astoria, Queens, has been added to the Phase II plans. A timeline for Phase II completion has not been announced yet.