This study aims to classify the geographical variants of Vulgar Latin found in the inscriptions of Pannonia Inferior, Dalmatia and Venetia et Histria, and their provincial capitals Aquincum, Salona and Aquileia, based on the changes of their consonant system in order to investigate the possibilities whether a regional dialect area over the Alps–Danube–Adria region of the Roman Empire could have existed as suggested by József Herman. For the analysis, the provincial countryside and the provincial capitals are contrasted to each other as well as to the rest of the Latin speaking provinces of the Roman Empire. The relevant linguistic data are taken from the Computerized Historical Linguistic Database of Latin Inscriptions of the Imperial Age, and the statistical analysis applies the Herman method of calculating the relative distribution of diverse types of non-standard data found in the inscriptions. After the comparison of the phenomena of sonorization, degemination, assimilation and /b/~/w/ fusion between an earlier and later chronological period, a suggested map of dialectal variants of Vulgar Latin in the region will be hypothesized.