HEIGHT=114 ALIGN=bottom>The first task here is to trace furrows, ripping up the maze of paths, and then excavate a deep trench in the ground. The second comprises refilling the trench with other material to make a foundation for the road build-up. The ground must not give way nor must bedrock or base be at all unreliable when the paving stones are trodden. Next the road metalling is held in place on both sides by kerbing and numerous wedges. How numerous the squads working together! Some are cutting down woodland and clearing the higher ground, others are using tools to smooth outcrops of rock and plane great beams. There are those binding stones and consolidating the material with burnt lime and volcanic tufa. Others again are working hard to dry up hollows that keep filling with water or are diverting the smaller streams.
The ancient Romans had a good system of roads, one which required systematic planning and maintenance. This project will look not at the layout of the roads of ancient Rome, but at their construction and makeup.
Cutting sections through ancient roads has been helpful to scholars studying the construction of Roman roads, though there is no truly standard construction. Surface analysis of existing Roman roads is additionally informative. Since it is not often possible to dig test trenches for a cross-section of a piece of road, we must rely upon the sections of ancient roads exposed in various quarries and other such works (Chevallier 86). It is economical, says Chevallier, to profile these roads magnetically, but he does not explain exactly how to do that (86); and as of this writing (1997), no systematic analysis by this means has been undertaken.
We can tell from an ancient administrative document of the first century, drawn up by the geometer Siculus Flaccus, that the Romans classified their roads in an order depending on their importance. The most important roads were viae publicae (public roads), which were funded by the state. Of secondary importance were viae militares (military roads), built at the expense of the army; these became public roads. Local roads, or actus, come after this; and finally there were privatae (private roads), built and maintained by the owners (Adam 277).
A Roman road is made up of a foundation and a surfacing, with varying contents. The Romans varied their road structure based on available materials and firmness of the subsoil. This disparity occurs even on the same road, and repairs on stretches of road further complicate interpretation (Chevallier 87). One of the first things Chevallier sets forth is that there is no one typical construction of roads in Roman times (86). Ironically, this is perhaps the primary unifying feature of ancient Roman roads, but there are some general characteristics that the roads share.
Back to the TopA Little Planning Goes A Long Way
The reason for these lengths is not that the Romans could not make curves, but it was easier to make the plan for the road in this way due to ancient surveying techniques. Margary explains as follows:
...sighting marks could be quickly aligned from one high point to another, with intermediate marks adjusted in between, probably by the use of movable beacons shifted alternately to right and left until all were brought into line; it is noteworthy that Roman roads nearly always make important turns upon high ground at points from which the sighting could easily be done (19).
He continues by saying that the road follows each alignment right up to the angle which is why the roads do not curve smoothly.
Back to the TopA Roman Road From the Bottom Up
The agger varies greatly in width and height; “it is sometimes just an earth bank, and in other places it may be very carefully built up in layers of stony or other material to the required height” (Margary 19-20). Most often, the agger is a small ridge, but on the most important routes it can be 4 to 5 feet high and 45 to 50 feet wide. Along even less important routes there is no agger and the road is set directly on the leveled ground surface (Margary 20). In effect, the agger constitutes the road’s foundation.
For the most part, this foundation contains a layer of “rubble” with stones laid in such a way as to provide drainage (Chevallier 86). Adam calls this bottom layer the statumen, “suitable for the foundations of any wall or floor.” He says that “on natural ground that had been leveled or dug in a wide trench, was placed a layer of stones laid on end, in rows. This solidified the base while aiding drainage” (277).
All material was derived locally, though if no suitable stone was available on the spot it might be brought from a few miles away (Margary 21). Margary says that this material for the agger was usually dug out of ditches on the side of the road, which he calls “scoop-ditches” (21). In stony areas, “there are often well-laid layers of big stones as a foundation for the surfacing,” which he says must have entailed quarrying along the way (Margary 21). This reliance on the immediate area is one reason for the variation in Roman roads.
Once we have constructed a solid foundation for the road, we can lay the road’s middle layer. Margary notes that the upper layers of the road are always laid carefully, “of finer material well-rammed down” (21). He says, “It is apparent from many well-preserved portions that this was often done in several successive layers, for if it is excavated for a section, the material can be seen to break away in flat slabs of gravel, etc., corresponding to these original layers” (21).
According to Chevallier, a layer of material such as sand is also a common part of this middle layer, serving to lend the road resilience (86). Adam calls this middle layer the rudus, a layer of “sand, or gravel and sand, sometimes mixed with clay” (277).
The topmost surface, or metalling, of the road varies; and most roads were defined by curb stones on each side (Adam 277). The ancient Roman roads are not always paved, especially along difficult stretches (Chevallier 87), but when available, the roads are paved at least with gravel (Margary 21). Flint and other small, broken stones are also used to pave the road (Margary 21), and Adam says that sometimes slabs of stone are used (277), though this did not appear before the beginning of the second century B.C. (Adam 278). “A text of Livy gives precise information that in 174 B.C. roads had to be paved in towns, but simply surfaced with sand or pebbles on country sections” (Adam 278).
Margary makes the following note, which is of interest: “In districts where iron was being worked, the hard slag [the waste metal created in producing iron] provided an almost ideal metalling, which seems in some cases to have increased its effectiveness by rusting together into an uncommonly hard concrete-like mass” (21). Chevallier confirms this with a citation from the work of the classicist Broise which says that some roads used iron slag, as a binding and sort of pavement. Some other roads were metalled with a sort of rough concrete; a combination of gravel bound with a little mortar. Where surfaces paved with stones are found, they are not presently bound; but it is likely that later road work has removed the binding (Chevallier 87).
As usual, there is great variation in the thickness of this upper layer. There are sections of road where the surface layer is only two to three inches thick, while some are one to two feet in the center and thin to a few inches at the sides (Margary 21). “At some points even greater accumulations of several feet have been recorded," but Margary attributes this to the build-up of repeated resurfacing or the filling in of low spots, such as a bridge approach, in order to make the road level (21).
Chevallier also quotes Broise in the discussion of road surfaces, saying that there are places where the excavated road is found to be a series of layers of gravel as thick as a meter, the result of numerous resurfacings (87). Adam says that the total depth of a road, from surface to the bottom of the base, could reach 1 to 1.5 meters (277). Also, the road surface is steeply sloped to each side from the center, in some places dropping as much as a foot on a road 15 feet wide--a considerable amount (Margary 21).
Much of this data has been provided by cross-sections of ancient Roman roads. Adam brings up an interesting public works project carried out in 1913 which required cutting deeply into a section of the via Appia. On page 278 he describes the head engineer’s account as follows:
He distinguished a first layer, one meter thick, of earth and gravel, originating from the neighboring mountain region, its width defined along the edges by two lines of large stones. On top of this was a thinner layer of gravel and crushed limestone, its width likewise defined by two rows of large stones, this time closer together. On top of this can be seen several layers of resurfacing of the same type.
Adam also lists the contents of a section of the via Flamina, which reveal at the bottom a compact layer of clay and pebbles, 20 centimeters thick, rammed into the natural ground that had been leveled. On top of this is another 20 centimeter layer of pebbles and stones mixed with clay under a surface of paving stones (278). Another example: “On the via Appia, 4.5 kilometers before Itri, a first layer of sand was covered with a thickness of crushed limestone into which slabs of lava 25 to 40 centimeters were fixed” (Adam 278). He also notes a place on the via Aurelia near Civitavecchia where the first layer was made of compacted tufa 40 centimeters thick. This was under a layer of gravel and stones also 40 centimeters thick and paved with slabs of lava (278). Such data illustrates the three distinct layers and also demonstrates the different materials used depending on what the land in the road’s immediate vicinity offered during construction.
HEIGHT=114 ALIGN=bottom>Intentional ruts are an interesting feature of some ancient Roman roads. While there are some ruts that developed from general use, there are others that are purposeful, between 6 and 30 centimeters deep, with sharp edges shaped by a pick or a point and hammer. Such ruts seem to have been used to guide wagons on difficult stretches of the road (Chevallier 89).
These ruts do not necessarily indicate the widths of the wheel-base of Roman vehicles, “for one can not be sure that the ruts form a true pair” (Margary 21-2). Adam says that the ruts would give the impression of the standardization of the distance between wagon wheels. “However, although an average of roughly 1.3 meters has been arrived at, the wide variations mean that a precise typology cannot be established” (279). Margary explains, “It is more likely that the outer wheel, being lower upon the camber of the road and so taking the greater weight, would score the surface more deeply” than the other wheel (22). Chevallier also notes that there are places where grooves are marked in the road to prevent horses from slipping (89).
From the ancient decrees of Augustus, we see that roads varied considerably in width depending on their function, importance, and the nature of the terrain, though Adam says there was no official criteria for road width (279). The widest roads, called decumanus maximus, were 40 feet, while byroads were 8 feet wide (Chevallier 88). In general, we may assume, the wider the road, the greater its importance. The general width of countryside roads was 20 feet to allow vehicles to pass, but all roads narrowed over difficult terrain (Chevallier 88-9). Such roads are sometimes wider than the width of two carts (one in each direction) because they were widely used. Margary lists all the travelers that used the roads, among them military leaders and their forces, high dignitaries, merchants traveling on business, and sick people seeking treatment, to name a few. He continues, “on the road all these folk would meet commercial traffic: foodstuffs moving towards the towns from the countryside, wares from local workshops, raw or finished materials on their way to far destinations...” (202). The list continues for nearly a page, indicating the amount of traffic the main roads carried and why such width was necessary. However, some mountain roads are too narrow (less than 3 meters) and too steep (over 15% grade) for carts and could only be used by beasts of burden (Adam 279).
In towns the road widths were also varied, though width is standard when the town planning conformed to a certain layout. “At Pompeii the main roads have an approximately uniform carriageway width (4 meters) and distance from wall to wall (8 meters)” (Adam 279). Secondary roads and alleys within the city are as narrow as 2 meters. The width of the street also varied depending on the surrounding buildings and whether there was a portico on the pavement (Adam 279).
Back to the TopAnother type of ditch is simply a strip of land on which cultivation and building were likely forbidden. This strip may have been for grazing. In some areas, the open strip may also have been a means of defense to prevent roadside ambush (Chevallier 88). Margary notes a “smaller type of ditch, presumably intended only to mark out a ‘road zone’ for the highway” (22). Such ditches are placed some distance away from the road and the agger is placed in the center of two ditches, one on each side, making the road area approximately three times the width of the actual embankment. “The ditches are small, only 2 to 4 feet wide usually, and quite shallow; and from their relation to the ground it is clear that they were not intended for drainage” (Margary 22).
Some of the roads are themselves depressed, such as those that traverse mountain passes. Unfortunately, no note is made of the depth of these roads. Other depressed roads are connected to what appear to be former military camps. Such depressed roads likely provided for the safe movement of troops or entry of supplies (Chevallier 88).
Back to the TopTwo rows of unconnected cross-beams were placed on the marshy soil for the whole length of the road. Each beam was 2 meters from the next one and there was a gap between the rows. Each beam came out 40 cm from the road and this projection had slots to pound stakes through the beam and into the ground. These beams supported two continuous rows of joists on top of which were laid a solid series of tree trunks. On top of the tree trunks were large, flat limestone flags, covered by road metal of gravel and pebbles (90).
Steep ground required a different solution. The roads followed a path such that major natural obstacles were avoided, but in following a direct path “it is inevitable that some local obstacles such as steep-sided valleys will be encountered.” To cross these, the road is turned along the side of the valley and continues in a zigzag pattern up the steep slope, and resumes its original path once the obstacle has been bypassed (Margary 19).
Romans were fortunate when building mountain roads that the road did not have to keep to a gentle incline. “An average hill does not necessarily present an obstruction to be tunneled through or bypassed” (Adam 280). The Roman engineers tried to use the simplest and most economical means, while letting the road depart as little as possible from a straight line (Adam 280).
“The most basic way of overcoming an obstacle, though not always the easiest, is to cut a passage through the rock for the route” (Adam 283). Such roads are generally found in mountainous regions and steep coasts. The Romans tried as often as possible to cut into only one side of the rock (Adam 283).
Adam says that a tunnel is the ultimate solution whenever cutting a path or going over or around the obstacle is simply not possible. He mentions the tunnel of Furbo on the via Flaminia which “begins by cutting into the rock face and then penetrates the rock for a length of 38 meters” (283).
The Romans also had to build some roads in the desert. These roads have left little physical evidence, says Chevallier, because their courses were mostly undefined except when crossing stony country (91). However, some “gently curving ridges” have survived, the remainders of small rocks and sharp objects pushed aside in order to protect the feet of the animals. The remains of wells and watchtowers are also found along dry desert routes (Chevallier 92).
In closing, it is most important to remember that the ancient Roman road consists of three layers: a bottom foundation layer, often of stone; a middle layer of somewhat softer material (such as sand or gravel); and a surface, or “metalling,” usually a gravel, sometimes paving stones. Roads were the arteries of ancient civilizations and building a road was a massive public work in Roman times. The ingenuity and industry of the ancient Romans is apparent through their road construction; and only through their continued study and preservation will we come to fully understand the capabilities and limitations of the ancient Romans.
