Searching for 20th century literature on roman wagon-technology is not an easy task. It is a well-known fact that most studies like the one I am doing here is missing a “handbook” saying what is to be said on the subject.
This said, a few authors actually have made some chapters in their books on the subject of transportation and even on land-transportation and wagon-construction, but water transport is still the hotter topic.
Concerned with ancient technology and therefore also writing on wagon-construction is K. D. White. “Greek and Roman Technology” and J. G. Landels “Engineering in the Ancient World”, both books being more than 20 years old and written without direct knowledge of the archaeological material. They leave out some important and interesting details on the construction, ex. the suspension system as discussed in earlier posts, but they do make 
use of roman carvings in the general analyses of wagons, but unfortunately not in discussing details in roman wagon-construction (Landels argues against the wagon-”pole” as being invented in roman times even though it is seen on carvings from the 3. century, see photo left).
K. Greene.”The Archaeology of the Roman Economy”, also 20 years old, discuss roman transportation from an economic point of view, and therefore the land-transportation is not left much attention. He believes carvings is no good in the research on roman wagons, so I am really looking forward to make a chapter on the use of roman carvings in my thesis.
I think we need some new editions of “Roman Technology” books, preferably new books on the subject! I do not know if anyone out there is writing a book on the subject right now, but if you do, please let me know and let us discuss the problems of roman land transportation and wagon-construction, and hereby eliminate the obvious errors in this field of research.
