How do archaeologists recognise a Roman road?
Roman roads are not always easy to find. Some still survive as raised banks or tracks, but others have been ploughed away, buried beneath later roads or identified only during excavation. An apparent straight line on a map is not enough to establish that a route is Roman.
To investigate a possible road, archaeologists compare several kinds of evidence: surviving earthworks, excavated surfaces and ditches, aerial photographs, LiDAR surveys, historic maps and the locations of known Roman military sites. Each can provide a clue, but the strongest conclusions come when several independent clues agree.
What did Roman roads look like?
There was no single Roman road design. Construction varied with the terrain, available materials and expected traffic. Where necessary, workers prepared a foundation, added stone or gravel and raised the surface above surrounding wet ground. A raised bank is known as an agger; roadside ditches sometimes helped with drainage.
The familiar picture of a neatly paved road made of large stone slabs should not be applied to every Roman road in Scotland. Many military routes were probably surfaced with gravel or other locally available material. A surviving agger may be more conspicuous today than the original surface.
How were the routes surveyed?
Roman surveyors could establish long, relatively straight alignments, but they also needed to deal with hills, boggy ground and river crossings. Some roads run in long straight stretches and then change direction at practical points in the landscape.
The groma was one Roman surveying instrument used to establish straight lines and right angles. Its general use is well known, but we should not assume which instrument was used on a particular Scottish road without supporting evidence.
What can aerial photographs and LiDAR reveal?
Aerial photographs sometimes show buried roads as cropmarks or soilmarks. LiDAR records small differences in ground height and can reveal low banks, terraces and cuttings that are difficult to see on the ground. It is especially useful when studying complex or wooded landscapes.
Neither method identifies a road as Roman on its own. A linear feature might be a later track, boundary or drainage work. Archaeologists must examine its form, setting and, where possible, dating evidence.
How can a road be dated?
Roads can be difficult to date because their surfaces often contain few finds. Excavation may establish whether a road overlies or is cut by a datable feature. Pottery or coins from securely recorded archaeological layers can also help, although they do not automatically date the initial construction.
The relationship between a road and an excavated fort can be important, but that does not always prove both were built at exactly the same time. A route might be repaired, extended or reused during a later Roman campaign.
Known, probable or possible?
Roman road maps often join isolated stretches to produce a continuous-looking route. It is important to distinguish between a road observed in excavation, a probable course reconstructed from several clues, and a possible alignment based on limited evidence. Some gaps remain unresolved.
The Gask Ridge offers a useful example of a military landscape in which roads, forts and watchtowers need to be studied together. The relationship between them is informative, but claims about the precise function of particular towers or routes still need to be tested against the archaeological evidence.
Explore the Gask Ridge, its road and watchtowers.
Could later roads follow Roman routes?
Some Roman routes remained useful after the army withdrew, and later roads can occupy similar corridors. But a medieval or eighteenth-century military road following a plausible Roman line is not, by itself, proof of continuous use of the same road surface. The age and construction of each section must be assessed separately.
The early surveys of William Roy are valuable because they recorded Roman remains when some earthworks were more visible than they are today. His observations are historical evidence, to be compared with modern fieldwork rather than accepted uncritically.
Investigate a Roman road yourself
- Is any stretch actually visible or excavated?
- Are there banks, surfaces or ditches?
- Does it connect securely identified Roman sites?
- Can its date be established, or is that inferred?
- Could a later road or boundary explain the feature?
- Which sections are certain, probable or merely suggested?
Use the Roman Roads in Scotland guide for the interactive route map, the principal roads and links to related sites. The lines on any reconstruction should be read as an interpretation of evidence, not as equally certain surveyed routes.
Further reading and sources
- William Roy, The Military Antiquities of the Romans in North Britain (1793), an important early survey, to be used alongside modern archaeological work.
- Historic Environment Scotland, Trove — archaeological site records and supporting references for individual road sections.
- Roman Roads in Scotland — the site’s main map, routes, research links and related articles.
