The Roman historian (i.e. scholar of Roman history) and archæologist FJ Haverfield, back in 1906, wrote:
“It would at first sight seem natural to identify Traiectus with Bitton and Abone with Seamills. This solution, however, raises serious difficulties. Seamills is indeed not much more than nine miles from Bitton. But Bitton is ten or eleven, not six, Roman miles west of Bath, and no ‘station’ except Bitton exists on this part of the route. Again, no ‘traiectus’ worth the name occurs near Bitton nor indeed anywhere on the route except at the crossing of the Severn. The first difficulty can be solved by supposing a corruption in the text, and reading xi. for vi.”
Is Haverfield’s calculation correct? The Roman mille passus is roughly 1.48km, or 0.92 miles, so vi, (or 6000 passus) as the Itinerary says, is about 8.9km or 5.5 miles from Bath, and, by my calculation, following the Roman road through Hanham, it is … 8.9 km and 5.5 miles (courtesy Google).
The distance from Sea Mills to Bitton is slightly more problematic, as the exact route is less clear; the Itinerary distance of 9,000 passus, or 13.32 km, 8.3 miles, is somewhat shorter than Google’s suggestion of 14.35km, 8.92miles. But Sea Mills and Bitton make reasonable sense in terms of distances.
Haverfield then goes on:
“The second [difficulty] has caused much perplexity. The remedy most often suggested is to transpose Abone and Traiectus, making Abone the name of the village at Bitton, which is within half a mile of the Avon, and identifying Traiectus with Seamills. Perhaps it would be better to suppose that Abone is Seamills and that Traiectus was put against it in the Itinerary: the double entry then was by error extended into two lines and Traiectus extruded the name corresponding to Bitton.”
So the main problem: Why is the Itinerary silent about the need to cross the Severn Estuary in order to reach Abone from Venta Silurum? Iter XIV is, after all, supposed to be an alternative to Iter XIII, a route from South Wales to Silchester via Monmouth and Gloucester, thus avoiding the crossing over the estuary. Here Haverfield’s suggestion initially makes sense: not to transpose Abone and Traiectus, thus making Traiectus Sea Mills, ‘the place at the crossing’ from Venta Silurum, and Abone being Bitton; but that Abone-Traiectus was a single place: Sea Mills. Which does then play havoc with the distances as given, and has already necessitated, in Haverfield’s view at least, amending one of the distances.
Other locations have been proposed for Traiectus: Aust, Oldbury-on-Severn, Keynsham, but this proposal would be that ‘traiectus’ is not a particular place at all, simply a verbal noun, indicating ‘here a crossing takes place’. Which is the next subject for investigation.