Classification yard

Some larger yards may put the lead on an artificially built hill called a hump to use the force of gravity to propel the cars through the ladder.

Some trains drop and pick up cars along their route in classification yards or at industrial sidings.

[1] Gravity yards were invented in the 19th century, saving shunting engines and instead letting the cars roll by gravity was seen as a major benefit, whereas the larger amount of manual work required to stop the rolling cars in the classification tracks was judged to be not that important.

They were later judged as inferior to hump yards because it became clear that shunting engines were needed anyway (at least in inclement weather like strong winds or icy temperatures when the oil in the bearings became thick) and because manual labor was getting relatively more and more expensive.

It is the heart of the yard—a lead track on a small hill over which an engine pushes the cars.

The speed of the cars rolling down from the hump into the classification bowl must be regulated according to whether they are full or empty, heavy or light freight, varying number of axles, whether there are few or many cars on the classification tracks, and varying weather conditions, including temperature, wind speed, and direction.

In the old non-retarder yards, braking was usually done in Europe by railroaders who laid skates onto the tracks.

Hump yards sometimes require unique locomotives; for example, there can be a risk of grounding with larger frames.

For this and other reasons, one can sometimes find locomotives specifically made or converted to work a hump yard.