LIKE YOUR COUSIN'S baby who's already talking at 9 months, Philadelphia's bike-share system is advanced for its age, having hit the 100,000-ride mark just two months after its debut.

Indego has around 600 bikes in its system of about 60 stations; it had only around 500 for its first month, making the six-figure milestone more impressive.

While a few more stations and bikes will be added in the coming months, the next big expansion of the system is planned for next spring, says Brodie Hylton, marketing manager for Bicycle Transit Systems, the contractor charged with implementing the system in coordination with the Mayor's Office of Transportation and Utilities.

Indego is expected to expand to 180 stations and 1,800 bikes, although exactly how big next year's growth spurt will be has yet to be determined.

That said, planning for that expansion already has begun, now that more reliable ridership data are being collected. Early ridership data are misleading due to curious riders trying out the system. The strong ridership numbers translate into reliable information for planners plotting where new docking stations will go.

Indego has reached the 100,000-ride club notably faster than similarly sized ride-share programs in other cities, arguing well for the program's continued popularity.

In Boston, the Hubway's 600 bikes totaled only around 75,000 rides at the two-month mark. In Washington, D.C., Capital Bikeshare hit only 80,000 by this time, despite starting off with 800 bikes. And Denver's program reached 100,000 only after seven months.

And while bragging rights over Boston, D.C. and Denver are always welcome, the big numbers matter for more important reasons, says Hylton. Indego is performing well on two key metrics: rides per bike per day (about three) and members per bike (around 10). Both numbers suggest a strong demand for the bikes.

Indego now has a little more than 4,500 active 30-day members, who pay $15 per month for unlimited free trips of up to one hour; and another 1,800 flex members, who pay $10 a year plus $4 per trip for up to an hour. Nonmembers also can walk up to a kiosk and pay $4 per half-hour.

Hylton credits Indego's relatively unique membership system for much of its early success. Other cities use annual memberships and more complicated pricing systems in which costs grow exponentially the longer you ride - fine for math-literate foreign tourists, but baffling to many Americans. Straightforward pricing and shorter memberships make it easier to try Indego and then get hooked.

"The barrier to entry is much lower here," says Hylton. "I think that helped us get our membership numbers up quicker."

In defense of the other cities, Philly had a couple of things going for it. First, bike share wasn't exactly a new concept when it arrived in April. Denver's system started in 2010, as did Washington D.C.'s - and D.C.'s was a reboot of an earlier, failed attempt in 2008. Boston launched in 2011, and New York's Citibike launched in 2013. Whereas other cities approached bike share with cautious curiosity, a fairly large number of Philadelphians were clamoring for Indego.