Trains carry a wide variety of goods, including heavy cargo that needs to be transported long distances. The most popular items for trains to transport include bulk cargo like iron ore or coal, containerization carrying shipping containers, and special cargo like cars or steel plates, which are not suitable for containers or bulk. Other types of cargo that trains carry include sand, gravel, limestone, granite, and other types of sedimentary rocks and stones, as well as vehicles, heavy machinery, manufacturing equipment, tractors, spare parts, and other related items. The cargo is referred to as freight or cargo, and it can be transported by truck, train, ship, or aircraft. In terms of which is most popular to carry freight, trains carry the largest percentage, 39.5 percent, in terms of miles and tonnage.