Those starting with z are direct special express passenger trains. Direct special express passenger trains are referred to as Zute, and the letter Z is the Chinese pinyin abbreviation of "Zhi". Direct express trains are not divided into inter-bureau and intra-regional trains, and use trains starting with Z plus the numbers 1-9998. The standard pronunciation of the railway system is "Zhi* times", and ordinary people are accustomed to pronouncing it "Z* times". After the fifth speed increase on April 18, 2004, direct special express passenger trains appeared for the first time, and the train numbers were prefixed with a Z (such as train Z161). Direct express trains can be divided into large direct express trains and small direct express trains according to whether they stop at the station. Dazhite: There are no stops in the whole journey, and the speed is very fast; Xiaozhite: There are no stops between the two major stations, and the speed is not as fast as that of Dazhite. "According to the train class: ordinary passenger cars, express trains (starting with K), intra-tube express trains (starting with N), express trains (starting with T), direct express trains (starting with Z), dynamic trains (starting with D) . Trains, also known as railway trains, refer to vehicles running on railway tracks, usually consisting of multiple carriages. They are one of the most important means of transportation in human history. Trains were also called steam in the early days. The locomotive runs on an independent track.