Strategic power/energy pipelines in the Civilization IV or (add-on) for a lot of the states, here have lot of variants of succession of events in region, and in the further can influence for the all world, etc.
Example modern world, the Russian gas is transported on the pipeline to the Europe, the power independence of the Europe under threat of, the Europe searches for an alternative route of energy resources to provide power safety of continent, Azerbaijan, Kazakhstan or Turkmenistan can solve power safety of Europe, here the formula is simple, the country the supplier; Turkmenistan / Azerbaijan / Kazakhstan, the country transit; Azerbaijan - Georgia - Turkey - the Balkans, the countries consumers; Georgia - Turkey - the Balkans
. and all the Europe, may be whole world. Russia jealously concerns to the given project, and further a trick.
Unlike roads and railways, the pipeline will be specific communication system, it is not be so many and will be tied only to power resourses, and will not cause difficulty in the management