Roads built by civil or military engineers from the 18th century onwards form an essential part of our heritage, but currently considered on a very infrequent basis. They represent one of the main turning points in the development of the transport system and serve to gain a better understanding of the historic construction of many landscapes and their current arrangement and operation. Their consideration as heritage has to be made on a territorial scale. This approach regards landscape as a cultural artifact, which is undergoing constant design, construction and transformation, where the road is considered as an axis that shapes the landscape and that contains individual elements such as associated structures or buildings. One of the most important characteristics of historic roads undoubtedly lies in the fact that they are a heritage that is still in use. Many of the roads built for carriages or the first automobiles have, in fact, served to trace the current network of roads and motorways. For this reason, many historic routes have undergone considerable modification and a large percentage of their heritage has disappeared. Likewise, their original or more intact sections, that is to say those that were replaced during their gradual adaptation to the automobile in the 20th century, are not always easy to identify. The distinction and undoubted documental value of historic roads, together with the neglect and vulnerability of these assets, makes it essential to define specific strategies with some degree of urgency in order to appraise this heritage. In this respect, the purpose of this article is to establish a methodology with which to identify sections of historic roads that were replaced by new alignments. The decision to focus the work on these sections is based on the fact that the infrastructure of these and particularly the older sections, have undergone a smaller degree of change and subsequently retain their original routing and geometry and a far higher number and variety of heritage elements more intact. This has made it possible to ascertain the diversity of elements composing the heritage of historic roads and enables the classification of the same. The identification methodology has been applied to a significant proportion of the Spanish main road network on selecting some 15 sections of historic roads of very different characteristics. Files have been prepared for each of these sections on the basis of cartographic analysis and detailed field work, these files including data related to location, characteristics and inventory of historic elements forming the road's heritage and will subsequently include references to road layout (both longitudinal and cross-sectional), structures (essentially drainage works), auxiliary elements (signalling) and associated buildings (inns, roadworkers’ houses…). Finally, and on the basis of the experience gained during the research, an initial proposal is laid out for the heritage assessment of these assets, considering aspects such as historic, technological and documental singularity which will depend on the degree of transformation and definition of the section in question.