Meng said there are not enough transit stations currently, which also adds extra passenger numbers in each train, and suggested that Beijing should learn from New York City, which has several lines in places with a high passenger flow to split the flow rather than adding more departures.
"For example, there is only one main station [Guomao] in the prosperous CBD area, which means everyone has to use it. Although Line 1 already has most departures, it still suffers great pressure," said Meng.
Large areas of the city are also not covered by the network, and sometimes citizens need to walk for a long distance to get to a station, he noted.
"To avoid such a situation and guarantee efficiency, the urban planning department should take both ground and underground levels into consideration," said Meng.
By the end of 2012, sections of four more subway lines will open, altogether 70 kilometers of new lines, making the whole network 442 kilometers in length, longer than London's network, which is 402 kilometers, said Jia Peng, spokesman of Beijing Subway.
The average cost of constructing subway lines in China is 500 million yuan ($80 million) per kilometer, the China Youth Daily reported in 2011.
By contrast, Singapore's new Circle Line cost $130 million per kilometer, a new line in Madrid cost $58 million per kilometer, while extensions to the subways in Paris and Berlin cost around $250 million per kilometer, according to The Atlantic in May, 2011.