Six weeks after Denver launched the first large-scale municipal bike-sharing system in the U.S., its popularity is rapidly growing.

Still, there is some confusion about how it works, and a few bugs need to get worked out.

Since the Denver Bike Sharing program, or B-Cycle, launched, nearly 8,000 registered users have signed up, including 830 annual members, for a network of 400 bikes available for use at 42 stations.

So far, the total number of B-Cycle checkouts is 16,500.

“It’s going very well, especially considering that late April and early May were extremely rainy, and it even snowed one day,” said B-Cycle spokesman Brent Tongco.

On Monday afternoon, Erik Wilsgard and Jamie Adams stopped at the Market Street station to get bikes for an afternoon ride along the bike path near Elitch Gardens.

“You can stop, dock the bike at REI, have coffee, then get a bike to ride back here,” Adams said. “It’s awesome.”

They’ve both used the bikes quite a bit since Denver Bike Sharing kicked off on Earth Day, April 22, and they understand how the system works.

It’s not bike rental, it’s bike sharing, which means that it’s designed for short, one-way trips. When you arrive at the destination, you dock the bike at the station so someone else can use it while you’re not. You then check out another bike for the return trip.

“Sometimes I notice that the bikes are locked up,” Adams said. “I think, ‘Oh, no, they should have docked those.’ “

While the bike sits there locked — instead of docked — a fee-based clock starts ticking.

Unlike the flat-rate daily fee charged by most bike-rental companies, B-Cycle riders pay membership dues.

A 24-hour membership costs $5, and the number of rides during this period is unlimited. But keep the bike undocked for more than 30 minutes at a time, and usage fees start to rack up — up to $65 a day.

Annual memberships are $65.

“We’ve seen in Europe that the average ride, in most cities, is 28 minutes,” Tongco said. “They realize that once they hit 30 minutes, they are charged a usage fee, and hopefully that will also translate here in the United States.”

To help people around the learning curve, the “Tour de B-cycle” kicks off today — a bike challenge where participants hit all 42 stations in one day, keeping all rides between stations to 30 minutes, so the only cost is the $5 fee.

“We want to encourage people to really explore Denver,” Tongco said. “On my test run, I rode past places I’d never seen. I dropped the bike off at Louisiana and Pearl. I’d never explored that before, and it’s a great way to see Denver in a new way.”

Some users also have had problems with the credit-card kiosks.

“There are a few hiccups,” Tongco said. “It’s a new system with new technology, and sometimes we have to reset the kiosks.”

Bike Share continually monitors the system to make sure each station has a good ratio of bikes and empty spaces to dock.

“A lot of times at 5 a.m. we take out a lot of bikes in a station to make sure that during the rush-hour commute, there are enough places to check in the bikes,” Tongco said.

To make things easier for people who use the system, there is an iPhone app that lists how many bikes and how many docks are available at each station at the current moment.

Adams loves the system so much that she hopes it expands rapidly and adds a station near her job at Presbyterian/St. Luke’s Medical Center.

“I could bike to work,” said Adams, a nurse who lives downtown near the 16th Street Mall. “I could make it in 15 minutes and just drop the bike off.”

Colleen O’Connor: 303-954-1083 or coconnor@denverpost.com