Traditionally, large shippers build factories and warehouses near rail lines and have a section of track on their property called a "siding" where goods are loaded onto or unloaded from rail cars. Other shippers have their goods hauled (drayed) by wagon or truck to or from a goods station (freight station in US). Smaller locomotives transfer the rail cars from the sidings and goods stations to a classification yard, where each car is coupled to one of several long-distance trains being assembled there, depending on that car's destination. When long enough, or based on a schedule, each long-distance train is then dispatched to another classification yard. At the next classification yard, cars are resorted. Those that are destined for stations served by that yard are assigned to local trains for delivery. Others are reassembled into trains heading to classification yards closer to their final destination. A single car might be reclassified or "switched" in several yards before reaching its final destination, a process that made rail freight slow and increased costs. Many freight rail operators are trying to reduce these costs by reducing or eliminating switching in classification yards through techniques such as unit trains and containerization. In many countries, railroads have been built to haul one commodity, such as coal or ore, from an inland point to a port.