The planning of transport infrastructure followed in the past the predicted transport demand. The challenges stemming from climate change and losses of biodiversity will force consideration of the increasing complexity of the transport system in future planning. Complexity research in natural science has developed strong concepts that show how natural organisms master complexity problems, recognized by recent Nobel Prizes in Physics and in Chemistry. Taking concepts like boundaries and folding as metaphors for treating complexity problems in transport infrastructure planning generates helpful lessons for its fundamental revision. It places the system’s view into the heart of the planning algorithm—instead of single projects—and stresses interactions within the transport system and between transport and interacting systems like economy, environment, and society. Appropriate methods for modelling dynamic systems exist in economics and transportation science but can further be developed analogously to the progress in natural science.

This chapter discusses some details of the climate impacts of the transport sector and their contribution to the external costs of the different transport modes. It looks at state actions to stimulate the market players in order to take avoidance measures and deals with concrete options for shifting transport from air to rail. The transport sector produces about one fifth of the global CO₂ emissions and shows high growth dynamics. In the aviation sector the emission trading scheme applies only to flights between airports in the European Economic Area. Savings of CO₂ emissions is the major external cost advantage of railways when compared with aviation. The railway sector has a long tradition of public subsidization since the state took over the governance in many countries by the end of the 19th century after spectacular bankruptcies of private railway companies and increasing importance for military purposes.