Cutting-edge technology
Achieving that standard has not been easy, and the success of the first test run on the 41-km line, on the morning of June 15, was a milestone in the development of China's subway capabilities.
"Most people saw the train has a designed top speed of 160 km/h, which is the fastest so far in the urban rail system in China," Yang said. "Usually, a city subway line has a top speed of 80 km/h to 120 km/h."
What most people have not noticed is that the carriages are different from those used on regular subway lines.
"The carriages are specially made for this line," said Mao Baohua, a professor at Beijing Jiaotong University who specializes in urban railway design. "They're the same size as the ones used on urban metro lines, but can travel as fast as a high-speed train. That means the cost is much higher than those used on previous lines."
An engineer working on the line, who declined to be named, said the carriages were made on the same platform as the country's CRH6 high-speed trains.
"The significance is that the adoption of the new carriage on the airport line has enlarged the application scenarios for China's high-speed trains," he said.
It's hard to tell from its appearance whether it's a high-speed train or subway train, he said, adding that it will lead to other urban subway lines using high-speed trains after necessary adjustments to infrastructure, and make such services more affordable.
Yang Guangwu, chief engineer of the Beijing Major Projects Construction Headquarters Office, said the new airport line's self-driving system will be the best in the world because it will also extend to checking, operational matters and cleaning, greatly reducing labor costs and increasing efficiency.
Even though Chinese law does not permit human-free driving and operation of subway trains and lines, the technology is already mature.
"The biggest benefit of the system is to raise the accuracy of stopping times, allowing more trains to run on the line during a certain period of time," Yang Guangwu said.
During test runs, trains on the new line have been departing every six and a half minutes.
According to the construction headquarters office, Beijing will apply the automated system on its new subway lines, including lines 3, 12, 17 and 19, which are under construction or on the drawing board.
Many other facilities on the trains illustrate the care taken in their design, and the progress made in China's subway construction capabilities, Yang Guangwu said.
For instance, there are wheelchair spaces and USB charging ports next to the passenger seats, along with variable-frequency air conditioners and LED lighting systems to save energy.
In the business-class carriage, all seats are equipped with tray tables and reading lights.
