PIPELINES

Pipelines are an extremely important and extensive mode of land transport, although very rarely appreciated or recognized by the general public, mainly because they are buried underground or under the sea as in the case of gas pipelines from North Africa to Europe. In the United States, for example, there are 409,000 miles of pipelines that carry 17% of all ton/miles of freight. Two main products dominate pipeline traffic, oil and gas, although locally pipelines are significant for the transport of water, and in some rare cases for the shipment of dry bulk commodities, such as coal in the form of slurry. Pipelines can even be used to carry small quantities of freight, such as in pneumatic tubes, but this use remains marginal and for short distances.

Pipelines are almost everywhere designed for a specific purpose only, to carry one commodity from a location to another. They are built largely with private capital and because the system has to be in place before any revenues are generated, represent a significant capital commitment. They are effective in transporting large quantities of products where no other feasible means of transport (usually water) is available. Pipeline routes tend to link isolated areas of production to major refining and manufacturing centers in the case of oil, or to major populated areas, as in the case of natural gas.

The routing of pipelines is largely indifferent to terrain, although environmental concerns frequently delay approval for construction. In sensitive areas, particularly in arctic/sub-arctic areas where the pipes cannot be buried because of permafrost, the impacts on migratory wild-life may be severe, and be sufficient to deny approval.

Pipeline construction costs vary according to the diameter and increase proportionally with the distance and with the viscosity of fluids (need for pumping stations). Operating costs are very low, however, and as mentioned above, pipelines represent a very important mode for the transport of liquid and gaseous products. One major disadvantage of pipelines is the inherent inflexibility of the mode. Once built (usually at great expense), expansion of demand is not easily adjusted to. There are specific limits to the carrying capacity. Conversely a lessening of supply or demand will produce a lowering of revenues that may affect the viability of the system. A further limit arises out of geographical shifts in production or consumption, in which a pipeline having been built from a location to another may not be able to easily adjust to changes.