Intermodal Transportation is the shipment of goods via ship, train, and truck in which the goods never leave their container. Instead the container is simply taken from ship to rail car, rail car to truck. This is done to reduce the handling of the actual cargo so that work at transportation hubs is more efficient and cost less.
The length of containers has been standardized by the International Organization for Standardization or ISO. While other lengths do exist container sizes are 20 feet, 40 feet, 43 feet, and 53 feet. In recent years the most common lengths for truck trailers and rail cars has been 40 and 53 feet. This is due to the fact that two 20 foot containers can be placed on a 40 foot carrier. 20 foot carriers are also the most common shipping containers that are received from Asia. As for 53 feet that is the standard length for US Semitrailers and can carry more goods than a 43 foot container. As a result the 43 foot container has seen a decrease in use.
Source: TTX Company