Abstract
France has developed a high quality motorway system that has been rapidly rationalised and matured in the late 20th century yet has been founded on ancient, Roman infrastructures. The development of the motorway system is thus an iterative method associated with hierarchical ‘top-down’ processes taking into consideration factors such as population density, network demand, location of natural resources, civil engineering challenges and population growth. At the opposite extreme to this approach is the development of transport networks within simple biological systems which are typically decentralised, dynamic and emerge from simple, local and ‘bottom-up’ interactions. We examine the notion, and to what extent, that the structure of a complex motorway network could be predicted by the transport network of the single-celled slime mould Physarum polycephalum. This comparison is explored through its ability to ‘deduce’ the French motorway network in a series of analogue and digital experiments. We compare Physarum network and motorway network topology in relation to proximity graphs and assess the trade-off between connectivity and minimal network length with a bottom-up model of a virtual plasmodium. We demonstrate that despite the apparent complexity of the challenge, Physarum can successfully apply its embodied intelligence to rationalise the motorway topology. We also demonstrate that such calculations prove challenging in the face of significant obstacles such as, mountainous terrain and may account for the missing route between Nice, Grenoble, Avignon and Lyon. Finally, we discuss the topological findings with respect to circle and spoke city planning infrastructures and certain species of web-building spiders.
Highlights
The French Motorway NetworkThe French motorway network is the fourth largest in the world comprising 11,882 km length of motorways, including 9048 km of toll highway (see data from ASFA (2014))
The emerging influence of centralised large scale planning, coordination and control of the motorway network is in contrast to the construction of transport networks employed by a wide range of simple organisms Bebber, Hynes, Darrah, Boddy, and Fricker (2007)
Plasmodium of P. polycephalum is cultivated in plastic container, on paper kitchen towels moistened with still water, and fed with oat flakes
Summary
The French motorway network is the fourth largest in the world comprising 11,882 km length of motorways, including 9048 km of toll highway (see data from ASFA (2014)). France’s motorway system has ancient origins - the first Roman roads of northern Gaul were established by Emperor Augustus (63 B.C. to 14 A.D.), who entrusted this task to his son-in-law Agrippa (62 B.C. to 12 B.C.) He started the creation of a vast hub-and-spoke network centred on Lyon, the new capital of Gaul, joining the confines of the Empire to the north, west and south. French motorways are both imprints of history and the logical consequence of network optimization They have been built in parallel with many national roads and in some cases they allow for more direct routes to major cities — including the displacement of the centre of gravity from Lyon to Paris. The concentric orbits around Paris that form its current, striking ‘spider-web’ configuration (Fig. 1) begin in 2000 and are ongoing, where radial axes join the major French cities without passing through Paris, such as the Lyon-Bordeaux and Nantes-Bordeaux motorways
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