Complex networks to understand the past: the case of roads in Bourbon Spain

The work aims to study, using GIS techniques and network analysis, the development of the road network in Spain during the period between the War of Succession and the introduction of the railway (1700-1850). Our research is based on a detailed cartographic review of maps made during the War of Succession, largely improving preexisting studies based on books of itineraries from the sixteenth century onwards. We build a new, complete map of the main roads at the beginning of the eighteenth century along with the matrix of transport costs for all the important towns describing the communications network. Our study of this complex network, supplemented by a counterfactual analysis carried out using a simulation model based on agents using different centralized decision-making processes, allows us to establish three main results. First, existing trade flows at the beginning of the eighteenth century had a radial structure, so the Bourbon infrastructure plan only consolidated a preexisting situation. Second, the development of the network did not suppose important alterations in the comparative centrality of the regions. Finally, the design of the paved road network was adequate for the economic needs of the country. These findings are in stark contrast with claims that the radial structure of the Bourbon roads was designed ex-novo with political or ideological objectives rather than economic ones. Our methodology paves the way to further studies of path-dependent, long-term processes of network design as the key to understanding the true origin of many currently existing situations.