Source: Adapted from William Black (2000) “An Unpopular Essay on Transportation”, Douglas Fleming lecture, Presented at the meeting of the Association of American Geographers, Pittsburgh, Pennsylvania.
Several alternatives, each having a specific topology, are possible to establish a level of service through a transportation network. Each topology is reflective of a level of network connectivity:
- (A) Minimum network. Represents the simplest configuration possible to link a set of locations, but has also the longest average path length.
- (B or C) Intermediate network. Represents a network topology seeking to find a compromise between the shortcomings of minimalism and the excess of redundancies. Hub-and-spoke networks are an attempt to rationalize services using a specific network topology (C). Mesh-like networks are also intermediate forms of connectivity. It is usually the maximum level of connectivity that a physical transport network can take.
- (D) Complete network. A highly redundant network with a complex topology which has an average path length close to the geographic barrier; the lowest possible average path length. These are usually abstract networks such as social networks and are very rare because of the complexity that this high level of connectivity would entail.