Roman roads

• 1. Introduction

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  Roman roads stretched across more than 400,000 kilometers at the height of the empire, stitching together 113 provinces through a web of 372 great highways. Twenty-nine military roads radiated outward from a single point in the capital, a gilded bronze monument Augustus erected in 20 BC near the Temple of Saturn. He called it the miliarium aureum, the golden milestone, and on it were inscribed the names of every major city in the empire and the distances to each. Constantine later named it the umbilicus Romae, the navel of Rome. That image says something worth sitting with: to the Romans, every road in the known world began at one spot, and that spot was theirs.

  What made this network so extraordinary was not just its scale but its durability. More than 80,500 kilometers of those roads were stone-paved, built to resist rain, freezing, and flooding, and engineered to need as little repair as possible. Some of those surfaces, and some of those courses, survived for thousands of years. Several are beneath the roads we drive today. So how did Rome build something that outlasted the civilization that built it? And what happened on those roads once they were built?

• 2. Stone Before Republic

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  The historian Livy mentions roads near Rome and their milestones at moments long before the first paved highway was laid. The Via Gabiana appears in references to around 500 BC. The Via Latina surfaces during the time of Gaius Marcius Coriolanus, around 490 BC. The Via Nomentana appears in 449 BC, the Via Labicana in 421 BC, and the Via Salaria in 361 BC. These were almost certainly leveled earthen tracks at that point, not the engineered structures Rome would later construct, but their names and their routes were already ancient by the time Rome's engineers arrived with their tools.

  The Laws of the Twelve Tables, dated to around 450 BC, already specified that a public road must be 8 Roman feet wide on straight sections and twice that width on curves. Later in the republic, widths of around 12 Roman feet became common for rural public roads, wide enough for two standard carts to pass one another without impeding pedestrians. The Tables also granted wayfarers the right to cross private land if a public road fell into disrepair, which made the ideological case for durable construction. Building roads that would not need repair was both practically sensible and a matter of civic principle.

• 3. Three Tiers of Road

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  Ulpian, the Roman jurist, divided the road network into three categories, and the distinctions carried real legal weight. The first tier, the viae publicae, were the great highways: state-funded, state-maintained, with their land vested in the empire. Siculus Flaccus, writing under Trajan between 98 and 117, described them as viae publicae regalesque, royal roads, placed under commissioners and repaired by contractors at public expense. Roads in this tier were named after the censor who ordered their construction. The Via Appia takes its name from Appius Claudius, who commissioned it in 312 BC. If a road predated the office of censor, or its origins were unknown, it took the name of its destination or the region it crossed.

  The second tier, the viae privatae, were country roads built by private landowners who could choose to dedicate them to public use. Features off the main roads connected to the main network by these secondary roads, which could be either paved or left as gravel surfaces. In North Africa, many prepared but unpaved roads fell into this category: viae glareae, roads to be strewn with gravel.

  The third tier, the viae vicinales, ran through villages and at crossroads, connecting settlements to one another or to the higher roads. Their public or private status depended on how they were originally funded. A privately built vicinalis road could become a public road once the memory of its private builders had perished. Their upkeep was the responsibility of the magistri pagorum, the magistrates of local cantons, who had the authority to require neighboring landowners to furnish labor or to repair at their own expense the stretch of road that passed through their property.

• 4. Engineering a Road

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  Building a via munita, the highest class of built road, began with civil engineers surveying the proposed route, followed by the agrimensores who laid out the actual roadbed. They used a rod and a device called a groma to obtain right angles. The gromatici, working like rod men, placed markers and defined a straight line called the rigor. When a surveyor could not see the intended endpoint, a signal fire was lit there to guide the alignment. The libratores then broke the ground, using ploughs and, with the help of legionaries, excavating a trench called the fossa down to bedrock or to the firmest available ground.

  Into the fossa went large quantities of rubble, gravel, and stone. Sometimes a layer of sand was placed first, if it was locally available. When the fill rose to within about a meter of the surface, the subsurface was covered with gravel and tamped down in a process called pavire. That tamped layer, the pavimentum, could serve as the road itself, or additional layers could be added. A foundation layer of flat stones set in cement, the statumen, could support a layer of coarse concrete, the rudus, then a layer of fine concrete, the nucleus. The top course of polygonal or square paving stones, the summa crusta, was crowned slightly in the center to shed rainwater.

  For obstacles, Rome preferred to cut through rather than go around. Long links in the network stretched as far as 55 miles. Gradients ran to 10-12% on ordinary terrain and 15-20% in mountainous country. Where a road passed above the Danube near the Iron Gates, it was carved half into the rock face to a width of about 5 to 5 feet 9 inches, with a wooden structure projecting out from the cliff to complete the road surface. That road served as a towpath, making the Danube navigable. The Tabula Traiana memorial plaque in Serbia is all that survives of it now, because the road itself is submerged.

• 5. Governance and Money

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  Building viae was a military responsibility, and the process carried a military name: viam munire, as though a road were a fortification. Under the republic, the task fell to consuls, with censors holding the broadest authority over streets and roads. Gaius Gracchus, as Tribune of the People in 123-122 BC, paved or gravelled many public roads and installed milestones and mounting-blocks for riders. Julius Caesar, appointed curator of the Via Appia in 63 BC, spent his own money freely on its repair. Gaius Scribonius Curio, as Tribune in 50 BC, introduced legislation making himself chief inspector of roads for five years.

  Augustus reorganized the whole system. Finding the existing boards of minor magistrates ineffective, he reduced the collegia of twenty-six magistrates down to twenty. He abolished the duoviri, the board overseeing roads outside the city walls, and effectively granted himself and future emperors the paramount authority that had once belonged to the censors. He appointed praetorians as road curators, each assigned two lictors, transforming what had been a temporary appointment into a permanent magistracy. He also designated curators of senatorial or equestrian rank for the great public roads, based on the relative importance of each road.

  Roads were not free to use. Tolls were collected, especially at bridges and city gates. Import and export taxes added further weight to freight costs. Maintenance fell to the provinces once a road was built, not to the central government. The curatores viarum handled fund-raising: they could ask private citizens to contribute, lean on high officials to distribute funds, and require censors to pay from their own money. When those sources fell short, taxes covered the rest.

• 6. Milestones and Maps

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  Milestones divided the Via Appia before 250 BC and most other roads after 124 BC. Each miliarium was a circular column set more than 2 feet into the ground, standing 5 feet tall, 20 inches in diameter, and weighing more than 2 tons. At its base was carved the number of the mile relative to its road. At eye height, a panel recorded the distance to the Roman Forum, along with information about the officials who built or repaired the road and when. These inscriptions are collected today in Volume XVII of the Corpus Inscriptionum Latinarum. Historians quickly began using milestones as reference points, noting the milestone at which a particular event occurred.

  Travelers who needed to plan a route consulted an itinerarium, which in its simplest form was a list of towns along a road and the distances between them. From that basic form grew the Tabula Peutingeriana, a schematic route-planner in which roads and branches were arranged roughly in parallel. Julius Caesar and Mark Antony commissioned the first known master road itinerary in 44 BC. Three Greek geographers, Zenodoxus, Theodotus, and Polyclitus, were hired to survey the whole system. The task took more than 25 years. The resulting stone-engraved itinerary was installed near the Pantheon, where travelers and itinerary sellers could copy sections from it.

• 7. Travel and Transport

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  Horse-drawn carts on Roman roads could cover 40 to 50 kilometers per day. A pedestrian managed 20 to 25. The most common vehicle for longer journeys was the raeda, a four-wheeled coach with high sides forming a box with notched entry points on each side. It carried several passengers with baggage up to a legal limit of 1,000 Roman librae, roughly 328 kilograms. A cloth top could be fitted for weather. A lighter vehicle, the cisium, was the cab of the Roman world, operated by drivers called cisiani and used for shorter journeys by one or two riders.

  For officials and non-military government travelers, the state maintained mansiones, way stations placed roughly 25 to 30 kilometers apart. Each was essentially a villa, and a permanent camp or town often grew up around them. Private travelers nearby had access to cauponae, inns that performed the same basic functions but carried a reputation for hosting thieves and prostitutes. Graffiti decorates the walls of the few that have been excavated. A more respectable alternative was the taberna, which had grown from the ancient custom of roadside houses offering hospitality on demand into something closer to a proper hostel. The Tabernae Caediciae at Sinuessa on the Via Appia kept a large storage room stocked with barrels of wine, cheese, and ham.

  Vehicle repair was handled at the mutationes, changing stations set every 20 to 30 kilometers, where wheelwrights, cartwrights, and equarii medici, veterinarians, were available. Using these stations as chariot relays, Tiberius covered 296 kilometers in 24 hours to reach his dying brother Drusus Germanicus.

• 8. What the Roads Carried

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  The cursus publicus, founded by Augustus, carried official mail by relay across the entire road network. A relay of horses could move a letter roughly 80 kilometers in a day. The postman wore a distinctive leather hat called a petanus and was a recognized target for bandits. Private mail for wealthier citizens was carried by tabellarii, an organization of slaves available at a price.

  Roman law in urban areas banned most wheeled vehicles during daylight hours. The Lex Julia Municipalis restricted commercial carts to nighttime access within the city walls and for a mile beyond them. Married women and government officials on business were permitted to ride within the city. These restrictions turned the roads just outside Rome into a constant flow of night freight, and the interior of the city into territory reserved for foot traffic and the carriages of those with legal exemption.

  Beyond Rome's borders the roads stopped. No paved roads ran outside the empire. In Britain, some pre-Roman ancient trackways existed before the legions arrived, among them the Ridgeway and the Icknield Way. The Icknield Way's name in Old English, Icen-hilde-weg, means "War-way of the Iceni," a parallel the Romans themselves drew to their own viae militariae. In Gaul alone, at least 21,000 kilometers of roadway were improved under Roman administration. In Britain, at least 4,000 kilometers. The network the Romans built in those provinces included roads still followed today, centuries after the last curator collected a toll or a postman in a leather hat made his rounds.