Passenger rail transport is one of the principal means of transport in the People's Republic of China, with rail passenger traffic exceeding 1.86 billion railway trips in 2011. It is operated by the China Railway Corporation (CR). The Spring Festival Travel Season is the peak railway travel season of the year. Passenger train classes and route identifiers Every train route has an identification number of two to five characters arranged by the Ministry of Railways. The first character can be alphabetic or numeric, while the second to fifth characters are all numeric. Trains are classified as either up (even-numbered) trains or down (odd-numbered) trains. Since the capital Beijing is treated as the focal point of the rail network, trains from Beijing are down services (e.g. the T109 from Beijing to Shanghai), while trains towards Beijing are up services (e.g. the T110 from Shanghai to Beijing). Trains that do not go either to or from Beijing are similarly designated up or down based on whether the railway they are traveling on would eventually lead them away from or towards Beijing. For example, the Z90 from Guangzhou to Shijiazhuang is an up service as it travels from Guangzhou in the direction of Beijing, but terminates in Shijiazhuang before reaching the capital. Some longer routes change from being an up service to a down service, or vice versa, mid-route, with more than one reversal being possible on the same route. In this case, the train would have two designations. For example, the G1202 and G1205 both refer to the same train from Harbin to Shanghai. From Harbin as far as Tianjin West Railway Station, the service is the G1202 up service traveling in the "up-direction" of the Beijing–Harbin High-Speed Railway towards Beijing, but after Tianjin West the train begins traveling away from Beijing down the Beijing–Shanghai High-Speed Railway towards Shanghai, becoming the G1205 in the process. Note: this is not to be confused with the G1208/G1205 from Qingdao to Harbin, which also switches at Tianjin West. The Z31/Z34 from Wuchang to Ningbo is a more complicated example. It starts as the Z31 down service from Wuchang to Zhuji, traveling away from Beijing. At Zhuji, it becomes the Z34 up service towards Beijing. However, one stop later at Shaoxing, it reverts to being the Z31. Types The preceding letter of route identifier indicates the type of the passenger train, often determined by the speed