The territorial structure of any region corresponds to a network of all its economic interactions. The implementation of networks, however, is rarely premeditated but the consequence of continuous improvements as opportunities arise, investments are made and as conditions change. The setting of networks is the outcome of various strategies, such as providing access and mobility to a region, reinforcing a specific trade corridor or technological developments making a specific mode and its network more advantageous over others. A transport network denotes either a permanent track (e.g. roads, rail and canals) or a scheduled service (e.g. airline, public transit, train). It can be extended to cover various types of links between points along which movements can take place. The relevance of a network is related to its connectivity. Metcalfe's law states that the value of a network is proportional to the square of connected nodes.