Sifting and Kicking
A locomotive is used to kick or push the car down rail and uncouple from it while in motion. The locomotive then stops and reverses away – leaving the car with enough momentum to roll away in the opposite direction. As the car continues to roll – switches and sidings are used to sift cars to the appropriate string.
Where the hump yard represents an automated classification process to build strings of cars – Sifting and kicking is a similar process done by hand.