The costs of transporting goods by different modes: A case study of pottery movement in late Roman Britain

There is a long-standing view that, in the Roman world, transport by sea and river was very much cheaper than by land. Previous analyses of transport costs have relied primarily on a few surviving historical records, notably the Edict on Maximum Prices issued by Diocletian in 301 CE. Here we outline an alternative method for deriving relative costs of transportation by different modes using materials recovered in archaeological excavations. We apply this to the distribution of Late Romano-British pottery (c. 250–400 CE) to calculate the cost ratios of transportation by road, river and sea to rural settlements and towns in lowland Britannia. The analysis suggests a best fit cost ratio of road to rivers and sea of 1:3:4 (i.e. transport by road was three times as costly as by river and four times that by sea), with 95% confidence interval of roads to rivers 1:1–5 and roads to sea of 1:1–9. These values are broadly consistent with transport cost ratios of 1:4:8 in England in the first half of the fourteenth century, when the country's transport network had reached a degree of integration comparable with late Roman Britain. • The ratio of transport costs by road, river and sea in Roman Britain are calculated. • Cost ratios are derived from the distribution of Late Roman pottery in Britain. • Best fit cost ratio for road to rivers is 1:3; 95% confidence interval, 1:1–5. • Best fit cost ratio for road to sea is 1:4; 95% confidence interval, 1:1–9. • Previous studies neglect numerous costs, over-estimating efficiency of sea transport.