Shipping agencies and shipowners rent whole containers to merchants or collect several smaller shipments together to fill one container destined for the same port. These are transported to and from the docks by means of specially designed railroad flatcars, as well as low trailers towed by truck.
The shipments have a considerably better chance to remain undamaged, since, during the journey, the individual pieces do not have to be moved one by one. The danger of going astray is not so great either, as the entire container is clearly addressed to the port of destination, and it is not easy to lose a 20- or 40-foot box.
On the docks, this has meant a revolution in the pace of loading. At a fully equipped container port, a container ship may be unloaded, reloaded and ready for the return trip within a day, whereas a conventional cargo liner, with half the capacity, could require a week or more for turnaround. A single container ship may thus replace four or more conventional cargo carriers.