Pipeline transportation is a long-distance transportation method that uses pipelines as transportation tools to transport liquid and gas materials. It is a specialized transportation method for transporting oil, coal, and chemical products from production sites to the market, and is a special component of mainline transportation in the unified transportation network. Sometimes, pneumatic tubes can also perform a similar task by compressing gas to transport solid compartments containing cargo. Pipeline transportation of petroleum products is more expensive than water transportation, but still cheaper than railway transportation. Most pipelines are used by their owners to transport their own products.