To define what before was called a "clear Roman class", here we have some considerations by Manuel Dúran Fuentes, major Spanish scholar of Roman bridges, expressed during the I congress on Roma public work, held in Merida on 11/15/2002, and that now onward we use to identify new bridges in the future.

"....in this duty of identification, not always a severe method has been followed and, quite often, some bridges were considered as Romans only because they have stone arches of an indefinitive ancient age, or simply because they were so called since a long long time. It's not right to call, as well, any other bridge of an uncertain age which stands in the same position where a Roman bridge used to stand. We do believe that this adjective should be reserved to those which owns the totality of the original masonry or those which, having only a part of this, the following reconstructions do not avoid to recognize it as a bridge of a clear Roman class".

Also Dúran specifies the parameters which permit to recognize of Roman class a bridge (percentage are reffered to the totality of Roman bridge in Hispania, the subject of his report).

Rules to define a Roman bridge: wider than 13,12 feet (95%) has a horizontal platform or with a ligthl "donkey back" (100% with no more that a 3% slope) construction in squared stone (100%) great uniformity of the height of the mouths (95%) wealth of holes in the masonry for the using of reinforcment clamps (67%)

( from Manuel Dúran Fuente's article published on the review "obra publica ingenieria y territorio" no.57)

In Signa Romanorum we use, as a basic quality of the monument, the following two characteristics :

- they have at least one vault remained

- the extension of the vault is equal or greater than 3 mts.

Structures which have not this last characteristic could be included as well, whereas they have a total number of arches not less than three. In this last case they should be better included in a new category called 'viaducts'.

Structural elements: