There are 14,000 bicycles for rent in the city, and they've been used 700,000 times. More than 20 million people live in Beijing. Public rental bikes have been sitting idle as not enough riders use the service, some using the rental areas to park their own bicycles or electric vehicles. Also, the bicycle lanes are often used by cars, making cycling a dangerous option. Public bike rental service, aimed at providing an alternative, low-carbon transport service to residents, was first tried in Beijing's Dongcheng and Chaoyang districts, which have high traffic flow, and the service was extended to Daxing and Yizhuang districts by the end of 2012.