A transmission line is a pipeline used to transport natural gas from a gathering, processing or storage facility to a processing or storage facility, large volume customer, or distribution system. A large volume customer may receive similar volumes of gas as a distribution center, and includes factories, power plants, and institutional users of gas. Often used to describe hazardous liquid pipelines also, a transmission line is a pipeline used to transport crude oil from a gathering line to a refinery and refined products from a refinery to a distribution center.