Trains are categorized by speed service In China. Different letters indicate different types of the train, including G, D, C, Z, T and K. The trains numbers with letter G, D or C are high-speed trains.
D-class (for Dongche simplified Chinese: 动车) trains are also called bullet trains with speeds of 200 - 250 km/h.
D-class trains service features EMU trains running at lower speeds, whether on high-speed or non-high-speed track. D-class trains can vary widely in actual trip speed. The D6009 train from Jinan to Qingdao on the Jinan–qingdao HSR, a line with designed speed of 250 km/h, averages 207 km/h for the trip
Because D-class train speeds are lower than G-class trains, its ticket prices are cheaper.