Abstract Energy is fundamental for present societies. In particular, transportation systems depend on petroleum-based fuels whose production levels are unsustainable. The inevitability of a peak of oil production (“Peak Oil”) is a now an accepted concept, although its date is still not consensual. In this work we discuss the peak of oil production and analyze the problems it will create. As much as can be inferred at this moment, the impact of the Peak Oil will certainly be significant but can still range from relatively benign to almost catastrophic scenarios. As a direct effect of Peak Oil, the increase in energy prices will be concentrated on the liquid fuels and the transportation sector will be specially affected. We believe that the cheap, wide-scale air transport that our present societies take for granted will revert to a more expensive and restrictive model closer to the selective commercial air transport of the early jet age. In our opinion the present road transportation systems will suffer an important transition that includes a reduced incidence of long distance road cargo movements, partially replaced by increased railway transportation, and, in terms of people commuting, a significant increase of mass transit and electrical vehicles. During this phase of forced adaptation, some countries will face greater challenges than others. However, the future of overall mankind and of particular countries, regions, or any groupings of people, is not yet fixed: it depends on decisions that are being taken at the present moment and on decisions that will still be taken in the future. As such, predicting the impact of the Peak Oil is something that must be done through a continuously refined process of information collection and analysis.