The structure and lasting impact of the Roman road system

This study builds a continent-scale, high-resolution digital map of 299,171 km of Roman roads and applies network-science and topographic analysis to answer three legacy questions: were Roman roads straight, how much do they persist in modern networks, and how central were major cities like Rome. The team measures slope, topographic position index, orientation and sinuosity on 1 km road segments and combines these spatial metrics with network-centrality measures and road-type classifications to quantify planning decisions and mobility roles across the Empire.

Results show Roman routes are generally low in sinuosity (mean 1.048, median 1.0045) and therefore straight where terrain permits, but they are slightly less straight than modern roads and become markedly sinuous in mountainous regions (notably southeastern Europe). Provincial capitals occupy more central positions for terrestrial mobility than ordinary settlements, and segments identified as principal roads function as stronger intermediaries than secondary ones. Finally, Roman road density correlates with the location of major modern roads, indicating a persistent imprint on later transport infrastructure, though regional data coverage varies and topography strongly conditions alignment.