Is it true that Beijing subway is supernatural?

Due to the busy operation of subway lines during the day, the maintenance of trains and other equipment is mostly carried out at night.

Empty train in the morning: In order to ensure the safe operation of the subway, a passenger-free train will enter the main line at both ends of the line before the first bus every day, and the train will slowly pass through the stations along the line without stopping, so as to eliminate the hidden dangers left by the construction and maintenance the night before and ensure the smooth and safe operation of the subsequent passenger trains.

Usually, an empty car that enters the main line before the first bus is called a raceway car.

Empty at night: most subway lines have parking lots and depots at both ends. Because the storage capacity and maintenance capacity of the parking lot and the depot are different, after the operation every day, the control center will allocate other vehicles back to the depot for cleaning, maintenance and storage under the condition of ensuring sufficient operation capacity the next day. Therefore, the empty train after running at night is actually just a return train.

There are also some cars idling at night because they have to debug various systems on the car, such as traction, braking and PIS.