The modern open-top hopper car is a bit more sophisticated than what they might appear.Today, the open-top version of these cars haul everything from coal to aggregates, such as ballasting (a term which refers to the crushed rock used under the railroad tracks that acts as support and cushioning), and feature a number of different drop-bottom designs to empty their cargo. You may then be asking, "What in the heck is the difference between gondolas and hoppers?" The drop-bottoms are basically what separate the two types. Whereas gondolas can look just like hoppers, right down to their size, length, commodity, and even a basic form of drop-bottom as well (which discharges material straight down) hoppers do not. Instead, they feature some type of angled or sloped chutes or hatches, which use the force of gravity to quickly unload their cargo and never requiring being tilted or turned upside-down in any way.