Holders of unused firm transportation contracts can resell this capacity in the secondary transportation market. Buyers and sellers in this market may be almost any participant in the primary transportation market, though pipeline companies are excluded because of their market power. Secondary transportation market came into existence in the US in 1992 when the FERC introduced a capacity release program requiring interstate pipelines to allow holders of firm transportation contracts to release or sell any unused portion of their pipeline capacity to other network users. The UK introduced a similar program of pipeline capacity resale in 1996 under the Network Code of British Gas. The resale of transportation contracts presents efficient allocation of transportation capacity. As a result of short-term changes in supply and demand some pipeline users will not utilize all their contracted capacity, while others will lack capacity to ship their gas. In the absence of a secondary market holders of unused capacity cannot sell it to those who need it. In so far as LNG terminals are concerned, when capacities at an LNG terminal are fully subscribed to under long-term contracts on the primary market, then often a new secondary market regime is put into place allowing to facilitate terminalling capacity exchanges on the secondary market in a multi-shipper environment. Under such a secondary market regime, all shippers owning terminalling capacity should inform the terminal in advance (e.g. at least two months in advance) of any slots they do not intend to use.