BEIJING -- As of the end of June, 31 cities on the Chinese mainland had urban rail transit in operation, with a total length of 3,965 km, according to the China Association of Metros.

Another 53 cities have started building rail transport facilities, with a planned construction length of over 9,000 km. About 5,770 km is currently under construction.

"Urban rail transit on the Chinese mainland has seen rapid development for over 10 consecutive years," said Zhou Xiaoqin, executive vice president of the association.

He said this year the length of urban rail transit in Beijing and Shanghai both surpassed 500 kilometers. Together with Guangzhou, their urban rail transit systems carry more than 50 percent of the total passenger volume of public transportation.

Urban rail transit will continue to be a priority of the country's urban infrastructure construction in the near future. It is estimated that the total length of Chinese urban rail transit in operation will reach 6,000 kilometers in 2020, he said.