What does "ballast" refer to in the context of railroad tracks?

In the context of railroad tracks, "ballast" refers to the material that is placed around and on top of the ties (sleepers) to provide stability and support for the track structure. This material, typically made of crushed stone or gravel, serves several important functions. It helps to distribute the weight of the trains on the tracks, maintains the alignment of the tracks, and facilitates proper drainage to prevent water accumulation that could lead to track erosion or other issues.

Ballast also plays a crucial role in keeping the ties in place, reducing movement and providing a solid foundation for the wooden or concrete ties upon which the rails rest. This stabilizing effect is essential for maintaining safe train operations and preventing derailments. Overall, ballast is a critical component of the railroad infrastructure, ensuring longevity and safety for rail transportation.