Xiao Nangying squeezed off the bus after a long working day in Hangzhou. Too exhausted to walk 20 minutes home in the dark, she borrows a bike from a rental point nearby her stop and gives it back 10 minutes later.

Chen Liang rides a bike carrying his bride, Wang Qian, during their eco-friendly wedding ceremony in Linyi, Shandong province, on Friday. Accompanied by nearly 60 bicycle riders, the newlyweds pedaled through city streets in honor of World Car Free Day, which fell on Saturday. ZHU WUTAO / FOR CHINA DAILY

"I can return it at a point in front of my community," said the 26-year-old woman. "There is no worry about it being stolen and it's very convenient."

Large-scale bike rental systems add an efficient option to the transport mix in major Chinese cities, thanks to their fleets of quality bicycles accessible via smart cards and from roadside, self-service docking stations.

The number of rental bicycles in Hangzhou, Zhejiang province, reached 65,000 in April, with more than 2,700 docking stations on street corners, every 300 meters, according to Hangzhou Public Transportation Group.

Last year, public bicycles were used more than 870 million times, of which 90 percent were by residents and migrant workers like Xiao.

"When my friends came to see me, we rented bicycles and went cycling around West Lake Park in Hangzhou," Xiao said.

Like Hangzhou, 60 other cities have adopted public bicycle rental systems. In Wuhan, Hubei province, more than 90,000 bikes are scattered across 1,318 docking stations.

Despite rising awareness of eco-friendly ways of living in cities, the development of public transport, especially bike rental, faces many difficulties.

Low profits

After paying an initial subscription fee, generally about 100 yuan ($16), users can pick up bikes and return them to any docking station in the city. The first hour is free, rising to roughly 1 yuan an hour thereafter.

According to Hangzhou Public Transportation Group, 96 percent of the 870 million times its bikes were used in 2011 were for just an hour. But every month, more than 2,000 bikes go for repair, said a report by Friends of Nature, an environmental NGO.

In many cities, the situation is similar. In Beijing, the revenue from rentals has been limited since the system began in June. "We have hardly made any profit in the past three months. The revenue cannot cover a month's salary for a single worker in our company," said Mu Liang, manager at GoldeNet Communication Technology Beijing, one of the two operators of the city's bicycle rental service.

Some companies have been forced to close due to lack of profits, among them Beijing Fangzhou Public Bicycle Co, formerly the largest bicycle rental firm in Beijing.

The company saw a peak during the Beijing Olympic Games in 2008, and it promised to set up a docking station every 200 meters. But it went bust in April 2010, with a 10 million yuan deficit.