Thirty-eight years ago today, on December 24, 1987 (November 4, 1987 in the lunar calendar), the Beijing Subway Exit Line was opened to traffic. On December 24, 1987, the long-awaited Beijing Subway Fuxingmen Exit Line was successfully completed and opened to traffic. There were two subways in Beijing at that time, one was the first-phase project operation line from Apple Garden to Beijing Railway Station, and the other was the second-phase project operation line from Fuxingmen to Jianguomen via Xizhimen and Dongzhimen. Due to historical reasons, there is no turnaround line in the middle of the first and second phases of the project, which is like "intestinal obstruction", which makes the subway ring line unable to operate in a circle, resulting in the first phase of the project transporting more than 500,000 passengers per day, which is in a "super-saturated" state, while the second phase of the project, which can only operate according to the horseshoe line, has only 40,000 to 50,000 passengers per day, and is in a state of "not getting enough to eat". After the turnaround line is completed, the first phase of the project subway trains can be turned back at the Fuxingmen, so that the ring line can be operated in a loop, including the South Ring, with a total length of 24 kilometers, running opposite the inner and outer rings, 4 minutes apart, and 40 minutes around the city. Passengers can transfer to each other in the in-app, and 436 trains run every day, which will It is expected to operate on the ring, and the daily passenger volume will be 800,000, which will play an important role in alleviating the ground traffic congestion in the capital.