英语翻译
These are the largest and most effective classification yards with the largest shunting capacity of several thousand cars a day.The heart of these yards is the hump:a track on a hill over which the cars are pushed by the engine after being uncoupled just before or at the top and then they roll,either as a single cars or some copuled cars together,by gravity into their destination tracks in the classification bowl (the tracks where the cars are sorted)