The carriages in Line 6 are equipped with numerous high-resolution sensing cameras, which will capture passengers' images and transmit them to an intelligent background system for analysis and calculation, which can identify whether passengers are wearing masks, waving for help or fainting, according to Beijing Subway Limited, the city's subway operator.

Above the carriage doors, new 4K high-definition screens display scrolling information of the stations along the line, transfer lines and passenger flows. "Compared with the previous board on the door, I can clearly see the information on the new screen at any position," said Wang Xiaoxiao, a passenger.

The carriage windows will also turn into screens showing the location, subway map and 3D demonstration of the next station when the train starts up.

Guiding screens are also installed in the waiting areas on the platform at one of the stations along the line to display information about the train's position, passenger density and air conditioning intensity in different carriages, according to Beijing Subway.

The sensing equipment is also installed in front of drivers, which can detect whether they are tired or distracted by monitoring their facial features and remind them with voice prompts.