Editing Roman roads (section)

====''Via munita''====
The best sources of information as regards the construction of a regulation ''via munita'' are:<ref name="SmithDictionaryAntiquities"/>
# The many existing remains of ''viae publicae''. These are often sufficiently well preserved to show that the rules of construction were, as far as local material allowed, minutely adhered to in practice.
# The directions for making pavements given by [[Vitruvius]]. The ''pavement'' and the ''via munita'' were identical in construction, except as regards the top layer, or surface. Pavement consisted of marble or mosaic, and ''via munita'' consisted of blocks of stone or volcanic rock.
# A passage in [[Statius]] describing the repairs of the [[Via Domiziana|Via Domitiana]], a branch road of the Via Appia leading to [[Naples#Greek birth and Roman acquisition|Neapolis]].

After the [[civil engineer]] looked over the site of the proposed road and determined roughly where it should go, the [[agrimensor]]es went to work surveying the road bed. They used two main devices, the rod and a device called a ''[[Groma (surveying)|groma]]'', which helped them obtain right angles. The ''[[gromatici]]'', the Roman equivalent of rod men, placed rods and put down a line called the ''rigor''. As they did not possess anything like a [[Theodolite|transit]], a surveyor tried to achieve straightness by looking along the rods and commanding the ''gromatici'' to move them as required. Using the ''gromae'' they then laid out a grid on the plan of the road. If the surveyor could not see his desired endpoint, a signal fire would often be lit at the endpoint in order to guide the surveyor. The ''[[libratore]]s'' then began their work using [[plough]]s and, sometimes with the help of [[legionaries]], with [[spade]]s excavated the road bed down to bedrock or at least to the firmest ground they could find. The excavation was called the ''fossa'', the Latin word for ditch. The depth varied according to terrain.

[[File:Via Munita schema.svg|thumb|upright=2.4|The cross-section of a street in  Pompeii.'''1''' Native earth; '''2''' ''Statumen;'' '''3''' ''Audits;'' '''4''' ''Nucleus;'' '''5''' ''Dorsum'' or ''agger viae;'' '''6''' ''Crepido'', ''margo'' or ''semita;'' '''7''' ''Umbones'' or edge-stones]]

The method varied according to geographic locality, materials available, and terrain, but the plan or ideal at which the engineer aimed was always the same. The road was constructed by filling the ''fossa''. This was done by layering rock over other stones. Into the ''fossa'' was placed large amounts of [[rubble]], gravel and stone, whatever [[Filler (materials)|fill]] was available. Sometimes a layer of sand was put down, if it was locally available. When the layers came to within 1 yd (1 m) or so of the surface, the subsurface was covered with gravel and tamped down, a process called ''pavire'', or ''pavimentare''. 

The flat surface was then the ''pavimentum''. It could be used as the road, or additional layers could be constructed. A ''statumen'' or "foundation" of flat stones set in cement might support the additional layers. The final steps utilized [[lime mortar|lime-based]] [[Mortar (masonry)|mortar]], which the Romans had discovered.<ref>{{cite book |title=The Ancient Engineers |last=de Camp |first=L. Sprague |author-link=L. Sprague de Camp |orig-year=First published 1960 |year=1974 |publisher=Random House |location=Toronto, Canada |isbn=978-0-345-32029-2 |pages=182–183}}</ref> They seem to have mixed the mortar and the stones in the ditch. First a small layer of coarse [[concrete]], the ''rudus'', then a layer of fine concrete, the nucleus, went onto the pavement or ''statumen''. Into or onto the nucleus went a course of polygonal or square paving stones, called the ''summa crusta''. The ''crusta'' was crowned for drainage.

An example is found in an early basalt road by the [[Temple of Saturn]] on the [[Clivus Capitolinus]]. It had [[travertine]] paving, polygonal [[basalt]] blocks, concrete bedding (substituted for the gravel), and a rain-water gutter.<ref>Middleton, J. H. ''The Remains of Ancient Rome''. London: A. and C. Black, 1892.  [https://books.google.com/books?id=k35LLSdsA78C&pg=RA1-PA251 Page 251].</ref>

[[File:RC174-Tabula Traiana.JPG|thumb|right|The remains of Emperor Trajan's route along the Danube in [[Roman Serbia]]]]
[[File:Engineering corps traian s column river crossing.jpg|thumb|right|Roman auxiliary infantry crossing a river, probably the Danube, on a pontoon bridge during the emperor Trajan's Dacian Wars (101–106)]]