BEIJING, Dec. 30 (Xinhua) -- Three more subway lines, including one for driverless trains, started operation in Beijing Saturday, bringing the total length of metros in the Chinese capital to 608 kilometers.
Located in Beijing's southwest suburbs, the Yanfang Line is China's first fully domestically-developed automated subway. It has nine stations on its 14.4-km main line, linking the areas of Yanshan and Fangshan. The line is expected to carry 70,000 passengers daily.
Also put into service Saturday is the 10.2-km Line S1, Beijing's first medium-low speed maglev line. It connects the western suburban districts of Mentougou and Shijingshan.
The third is the 9-km West Suburb Line connecting tourist spots, including the Summer Palace and the Fragrant Hills in northwest Beijing.
Beijing now has 22 metro lines.
According to Beijing Transport Institute, the length of the city's subway increased by 400 kilometers in the last nine years. In 2008, the year Beijing hosted the Summer Olympic Games, it had eight lines, totalling 200 kilometers.
"Passengers make 10 million trips by metro every day in Beijing. The metro network is truly a non-stop underground city," said Li Haitao, deputy director of the metro law-enforcement division of the Beijing transport law-enforcement squad.
In 2015, Beijing established the division to ensure the safety of metro lines. Now it has 700 staff.
"There is great danger when there is large amount of passengers in rush hour. We are under a lot of pressure to ensure the safety of the metro network," Li said.
The Pingguoyuan stop on Line 1, Tiantongyuan stop on Line 5 and the Shahe stop on the Changping Line are among the busiest stops. "Over 20,000 passengers go through a single stop during the morning rush hour," said Jia Peng, a spokesman for the Beijing Subway.
The subway operators have improved signal systems to cut the intervals between trains.
"The interval of one minute and 43 seconds on Line 4 is the shortest in China now," said Zhong Guoliang, vice general manager of Beijing MTR Corporation, operator of Line 4 and others.
"Explosive growth of the population in Beijing has strained the capacity of the metro lines. Some lines reached their long-term designed passenger capacity when they started operation," Zhong said.
The first metro line, Line 1, running between the city's east and west, started operation in 1969. According to Beijing Municipal Commission of Transport, Beijing will have 900 kilometers of metro lines by 2020.
"By then, the lines will better meet the transit demand of the people in the capital," said Rong Jun, deputy director of the commission.