Chinese trains are divided according to their speed into various classes, identified with different letters and numbers. The letters refer to different classes:
G and D Trains, G (Gaotie) and D (Dongche) series trains both use CRH (China Railway High-Speed) railways.
G trains is the fastest running for long distance in China, the top speed of which could reach 350km/h. Currently, the G-train could finish the 1,068-kilometers Wuhan-Guangzhou High-Speed Railway in 3 hours, the 301-kilometers Shanghai-Nanjing High-Speed Railway in 73 minutes and the 458-kilometers Zhengzhou-Xian High-Speed Railway in 2 hours.
D trains are next fastest with a maximum speed of 250 km/h, and second most expensive. The facilities of G and D series trains are similar, all new and modern, like the train from Guangzhou East railway to Shenzhen Lohu
They provide frequent services between first-tier cities, many state capitals and major cities, such as trains from Beijing to Guangzhou, Beijing to Shanghai, Beijing to Xi’an, Beijing to Zhengzhou, Guangzhou to Shenzhen, Shanghai to Hangzhou, Shanghai to Nanjing, and so on. They only stop at a few major stops along the way, and some of them provide non-stop services.
C – Intercity EMU
This is also the fastest kind, but runs for short travel distance between two nearby cities, such as Guangzhou–Zhuhai Intercity Mass Rapid Transit.