The train starting with Z: the direct express passenger train, referred to as Zhite for short. The letter Z is the Chinese phonetic abbreviation for the word "Zhi". This kind of train must stop at one stop during the trip, or stop at one stop but do not handle passenger service. The bottom of this kind of train is 25T, and they are all air-conditioned trains. All through trains run across bureaus (not in a railway bureau). This kind of train appeared after the fifth speed increase on April, 2004 18. Although there used to be through trains, they were all mixed in express trains. D stands for bullet train, G stands for high-speed rail, T stands for express train, and K stands for quick air conditioning. D, G, Z and K are all trains, but the types of trains are different.

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Regarding the numbering rules of China railway trains, the numbering rules of China railway trains are to distinguish trains in different directions, different types, different sections and different times, and arrange an identification code for each train, that is, the train rules. The number of trains is expressed in Arabic numerals, and the Arabic numerals should be added before the number of trains, and the first letter of the Chinese phonetic alphabet of the train type should be added.

In order to ensure traffic safety, maintain transportation order and standardize train codes, the former Ministry of Railways stipulated that the whole line, branch line to trunk line or designated direction into Beijing should be the upward direction, and the train numbers should be even; On the contrary, it is the downward direction, and the number of trains is odd.