Roman road: Encyclopedia II - Roman road - Construction of a Road

Roman road - Construction of a Road

Roman road - The Team

The distinction between staff and line officers applied to the Roman army as well. Among the staff officers were a unit called the architecti, "chief builders", responsible for all military construction, which road-building was. These were required to be educated men. Geometry, of course, was a central requirement of their education.

The architecti had a full-time staff of agrimensores ("land surveyors") and libratores ("levellers"). The teams of construction workers were taken ad hoc from the ranks of the legionaries. In addition to his arms, his rations and his utensils, every soldier carried a saw, hatchet, sickle, pick and spade. Augustus decided as a matter of policy to keep the soldiers busy (and therefore out of trouble) by turning them to construction. This labour improved their strength and stamina, rendering them almost unbeatable, but elicited constant complaint about the back-breaking work, which sometimes turned to mutiny.

As might have been expected, the legions sought involuntary assistance for their hard labor. Slaves, prisoners of war and convicted criminals often performed the most difficult tasks of quarrying and transporting stone. They were also used for road repair. Whether they performed these tasks in chains is not known. Whipping, however, was common, for which the verb was verberare. Beatings were by no means confined to slaves. Indeed, one of the symbols of Roman authority was the fasces, a bundle of whips.

Roman road - The Method

The Romans are believed to have inherited the art of road construction from the Etruscans. No doubt the art grew as it went along and also incorporated good ideas from other cultures.

After the architect looked over the site of the proposed road and determined roughly where it should go, the agrimensores went to work surveying the road bed. They used two main devices, the rod and one called the 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 transit, an architect 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.

The libratores began their work. Using ploughs and legionaries with spades, they excavated the road bed down to bed rock or at least to the firmest ground they could find. The excavation was called the fossa, "ditch." It was typically 15' below the surface, but the depth varied according to terrain.

The road was constructed by filling the ditch. The method varied according to geographic locality, materials available and terrain, but the plan, or ideal at which the architect aimed was always the same. The roadbed was layered.

Into the fossa was dumped large amounts of rubble, gravel and stone, whatever fill was available. Sometimes a layer of sand was put down, if it could be found. When it came to within a few feet of the surface it 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 concrete, which the Romans had exclusively rediscovered. They seem to have mixed the mortar and the stones in the fossa. First a several-inch layer of coarse concrete, the rudus, then a several-inch 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, such as you see in the picture, called the summa crusta. The crusta was crowned for drainage.

It is unclear that any standard terminology was used; the words for the different elements perhaps varied from region to region. Today the concrete has worn from the spaces around the stones, giving the impression of a very bumpy road, but the original surface was no doubt much closer to being flat. These remarkable roads are resistant to rain, freezing and flooding. They needed little repair.

Roman road - Surpassing Obstacles

Roman architects preferred to engineer solutions to obstacles rather than circumvent them.

River crossings were achieved by bridges, or pontes. Single slabs went over rills. A bridge could be of wood, stone, or both. Wooden bridges were constructed on pilings sunk into the river, or on stone piers. Larger or more permanent bridges required arches. Roman bridges were so well constructed that many are in use today.

Causeways were built over marshy ground. The road was first marked out with pilings. Between them were sunk large quantities of stone so as to raise the causeway 6 feet above the marsh. In the provinces, the Romans often did not bother with a stone causeway, but used log roads (pontes longi).

Outcroppings of stone, ravines, or hilly or mountainous terrain called for cuttings and tunnels. Roman roads generally went straight up and down hills, rather than in a serpentine pattern. Grades of 10%-12% are known in ordinary terrain, 15%-20% in mountainous country.

Roman road - Financing

Financing road building and repair was a government responsibility. The officials tasked with fund raising were the curatores viarum, in which you can see the English word, curator. They had a number of methods available to them. Private citizens with an interest in the road could contribute to its repair. High officials might distribute largesse to be used for roads. Censors, who were in charge of public morals and public works, were expected to fund repairs sua pecunia. Beyond those means, taxes were required.

The beauty and grandeur of the roads might tempt us to believe that any Roman citizen could use them for free, but this was not the case. Tolls abounded, especially at bridges. Often they were collected at the city gate. Freight was made heavier still by import and export taxes. These were only the charges for using the roads. Costs of services on the journey went up from there.

Adapted from the Wikipedia article "Construction of a Road", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki