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date: 29 June 2022

traffic, urbanfree

traffic, urbanfree

  • Eric Poehler


The movement of people, animals, and vehicles through the ancient urban environment had a significant impact on the shape of ancient cities, but as an object of study, urban traffic is a relatively recent area of interest, one that has tended to focus on the Roman world. The range of methods available to consider the topic, however, are relatively many, including literary analysis, archaeological field survey, and a battery of technical methods, such as Space Syntax, Network Analysis, and Agent-Based Modeling. In all of these approaches, two models of movement—pedestrian and vehicular—remain paramount. The results of studying urban traffic have shed new light on the impact of different forms of urban design, the ways in which ancient people navigated those designs, and norms and formal systems in place in urban environments to order the movement of people and vehicles.


  • Roman Law
  • Roman Material Culture

Whether on foot or borne by animals or vehicles, the movement of people and goods through ancient cities shaped those cities and the lives of those within them. The clustering of humble shopfronts on commercial streets and the monumental facades of processional routes alike owe their character to the passage of people moving for different purposes along their lengths. Indeed, as one of the most common elements of everyday urban life, interest in wheeled and pedestrian traffic consequently has become more defined in the classical world as greater attention is paid to non-elites and their material culture. Urban traffic is in fact another window onto everyday life, opening up opportunities to examine the reciprocal effects of city plans and their architectural elaborations on the political, economic, and social landscapes draped over them.

Specifically, movement is an important variable in the analysis of the urban fabric, one that complements previous research on city plans and literary descriptions of ancient urban life. In concert, these forms of evidence now permit us to model the movement potentials of different urban plans from different regions and historical eras (e.g., Pompeii and Perge), to evaluate long-debated notions of traffic control (e.g., the daytime ban on carts in Rome), and even show that (at least) the Romans, as a rule drove on the right and even implemented one-way streets, but did contravene these rules when circumstances allowed and/or required it. Interest in and evidence for ancient traffic, however, is not distributed equally, and most of our sources of information come from the Roman world in the imperial period. Evidence from Pompeii and Italy more generally dominates, though North Africa and Asia Minor have many urban sites were some evidence for urban traffic survives. What we can say about the topic today therefore reflects these limitations of chronology and space.

Approaches to Urban Traffic

The study of ancient movement is necessarily conducted through proxies. Many of these proxies are archaeological in nature, though literary evidence is indispensable for revealing the meaning of travel, for process of way finding, and for especially for contextualizing other proxies.1

One of the earliest attempts to model traffic using the remains of an urban environment was Laurence’s doorway occurrence method, which used the number of doorways along a street to generate maps of relative intensity of movement that these doors anticipated.2 Although Laurence’s method generated significant debate, other spatio-statistical methods, especially Space Syntax, became more common and were applied at several urban centers in the Greek and Roman worlds.3 Space Syntax measures the degree to which a street network is interconnected and how well, therefore, it facilitates movement throughout that network. Most ancient cities, however, are only partially excavated, and recent attempts to apply Space Syntax to urban plans known mostly though geophysical prospection are revealing new results.4 There are many important critiques of this method in general, but the relatively small scale of most ancient cities and the general uniformity of their grid plans tend to yield predictable results.5 A related approach, GIS Network Analysis, has also been deployed within ancient cities, but more often between them.6 One recent study calculated more than three million paths across Pompeii, but difficulties in modeling the unexcavated parts of the city and especially the ways in which humans transit the urban landscape diminished the results.7 Another technique, Agent-Based Modeling, which is dedicated to more accurately representing the aggregate choices of humans within their environments, would seem to be a way forward. To date, however, few studies on urban traffic have been published.8

Literary studies of urban traffic have undertaken the equally difficult task of identifying social and historical information in the imagined journeys across ancient cities, Rome in particular.9

The more general of these studies have also focused on streets and their character to define something of the quality of the movement they carried. Several scholars have looked closely and in context at the Greek and Latin words that refer to urban passages, defining them into categories—broader, more public streets v. narrower, more secluded streets—and associating these types with the varieties of behavior along them.10 Though often written to impart different information, textual evidence offers variety, color, and purpose to ancient travelers that the archaeological and statistical methods do not.11 Particularly valuable are the attempts to understand ancient wayfaring from literary and papyrilogcial evidence.12 These studies offer not only an image of the urban streetscape, but also a glimpse into how ancient people saw, understood, and utilized that image to parse and share spatial and directional information.13

Many of these methods do not differentiate between wheeled and pedestrian traffic, though some of their evidence (e.g., doorways) tends to skew toward the latter. Research on vehicular traffic in urban environments has focused on three classes of evidence: the size of the city’s streets, the ruts worn into street surfaces, and the shapes and intensities of wearing on other street architectures. A seminal article by Tsujimura combined the first two and defined the minimum widths for a street to permit two lanes of traffic along with the depth of rutting along each street. She also considered the distribution of curved ruts at intersections to argue for the existence of a traffic system at Pompeii.14 Poehler has supported this claim with a description and analysis of the third class of evidence, which reveals the direction that (most) ancient traffic was moving on a particular street.15 Additionally, this study shows that, while directional wearing patterns (like rutting) are nearly ubiquitous in ancient cities and available for interpretation, systems of traffic are not yet attested elsewhere.

Urban Traffic and the Regulation of Street Form

Even in its earliest formulations as a political body, Romans were interested in defining the physical shape of their city and the condition of its corridors of movement. Within the fragments known of the Twelve Tables (VII 6–7) are statutes that describe minimum widths of roads (8 Roman feet, 2.36 meters) and twice that distance on a curve.16 Such a narrow minimum width for a street, sufficient for only one direction of vehicular travel at a time, suggests that, in the 5th century bce, traffic was primarily pedestrian or by mule and that vehicles were relatively few. By the late 3rd century bce, however, the volume of urban traffic of all types had increased and the condition of the street surface rose to prominence in the public imagination. Thus, we learn that in 238 bce a prominent street, the clivus publicus, was remade and only half a century later (174 bce ), public officials would claim to have paved all of Rome’s streets in stone.17

In the following centuries, epigraphic evidence from across Italy attests the continuing interest in stone paving and the renown that could be achieved by providing this urban infrastructure.18 Although there are undeniable aesthetic aspects to pavements, the practical benefits of such solid surfaces for the movement of people and goods cannot be overlooked. Moreover, the proliferation of paving across an increasingly urban Roman world suggests an equivalent increase in the volume of traffic within those environments. By the end of the Republic and into the early Empire, these gifts of pavement would become the responsibility of local magistrates, and we see in municipal charters and statutes their duty to maintain and improve the streets.19 Both Ulpian and Papinian are explicit that the purpose of street maintenance is to permit the free flow of movement in the city.20 During the Empire, even the emperors would take on and finance major paving projects, both inside cities and out.21

Walking and Driving

Urban traffic in the ancient world can be divided into two forms, pedestrian and vehicular, (including riding in carts and wagons and on animals), and we see this division clearly in the legal, literary, and material evidence. The most notable legal division is found in the lex Iulia Municipalis, which describes the restriction of vehicular traffic to night time travel, leaving the city (mostly) free for pedestrian movement throughout the day. Although disagreement about these lines continues, the notion that the Romans sought to divide urban traffic in these ways is not.22 Later imperial decrees show that this distinction continued to be extend and refined. Claudius proclaimed that travel through cities was only to be on foot or (by being carried in a litter), and Domitian ordered the sidewalks cleared to facilitate pedestrian movement.23 Hadrian explicitly forbade the riding of horses and overloading of carts, and in the reign of Marcus Aurelius, Claudius’s ban was reinstated.24

The physical segregation of urban traffic between pedestrians and vehicles is also identifiable in the design of city gates at the edges of a city and in development of sidewalks and pedestrian zones within a city. By the mid-1st century bce, bipartite and tripartite gates were built with passages dedicated to each type of traffic. Later, wheeled traffic would also be subdivided, presumably by direction, in gates with four portals. A similar urban change was taking place at about the same time inside cities as buildings encroached onto roadways and flanking footpaths—sidewalks—were constructed. Like stone street paving, these features were introduced first by private initiative and primarily for private aggrandizement. As the form spread at places like Pompeii, where we can trace their development, so too did the public expectation for such conveniences. By 79 ce, there was not only a patchwork of different street surfaces, but also a wide range of elevated (ca. 30cm) sidewalk types, ranging from a single line of curbstones, to broad sections of decorated cocciopesto, to pebble and tessellated mosaics.25 More than three hundred stepping-stones provided pedestrian crossings between these elevated sidewalks and kept pedestrians out of the street proper, which had double-duty as Pompeii’s surface drainage system.

With the proliferation of under street sewerage in the 2nd and 3rd centuries, stepping-stones would disappear along with the need for them, but the segregation of urban traffic continued in the development of the colonnaded avenue. These grand, urban monuments spread across the Roman world, and especially in the east, to become emblematic of late antique urbanism.26 At Antioch, Libanius described one of the most well-known colonnaded streets as teaming with shops and commercial activities, such that pedestrians were as a river, and perhaps absent of vehicular traffic.27

Despite these many ways of segregating urban traffic, one should neither imagine a rigid division in daily life nor a strictly linear evolution of increasing control over the street. For Rome (at least) of the 1st century bce, The lex Iulia Municipalis exempted a few types of official traffic, permitting them to circulate during the day.28 Some have even interpreted this to include all passenger traffic.29 At night, however, the street was a scene filled with all manner of traffic and ripe for lampooning by satirists.30 Whether or not this law was in force in other cities in the later 1st century ce, the volume of wheeled traffic at Pompeii was sufficiently low that most vehicles could drive in center of the street, leaving room for pedestrians to escape the sidewalks. In the 4th century ce, at Perge, one side of the double lane colonnaded boulevard was co-opted for pedestrian space, with monuments built on top of the street pavers. At Ephesus, however, evidence shows that vehicles invaded the colonnades of the upper agora.31


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