Hello.

So as with many things related to daily life in Ancient Greece and Rome we don’t have a complete picture, but there is a surprising amount of evidence that we can use (and as you’ll see there has been some really ingenious research to supplement our understanding) that shows that yes there were rules and regulations. The picture that we have is that the state set general standards and regulations, but with different cities and regions having their own rules (called the leges municipales, likely administered by local magistrates). Arguably the most famous state decree concerning traffic is to be found in the Lex Julia Municipalis (the Julian Law concerning Municipalities) that set provisions for the policing of the city of Rome. This has traditionally been linked to Julius Caesar, and bans the traffic of “heavy wagons” in the city during daylight hours “in the daytime, after sunrise or before the tenth hour” (Tilburg, 2007), but does still allow many commercial vehicles to continue moving in the city and set exceptions for the Vestal Virgins and other priesthoods. The idea then seems to be to regulate the flow of traffic into the city by restricting the use of vehicles to strict commercial or religious purposes, clearly because the traffic had become an issue in Rome. However, this does not seem to have been completely successful, as there are ancient authors such as Juvenal (3.236-61) who complains about the unbearable noise caused by the constant traffic, which includes heavy pedestrian traffic. It seems like sitting in traffic jams and (as you pointed out with the reference to Oedipus) road rage are actually an ancient pastime! The next time you beep at someone for cutting you up on the road remember you’re following your ancient ancestors! Other general regulations seem to be that commercial goods were distributed mostly at night, likely to avoid further congestion but also for carts to travel unimpeded in what would most definitely be heavy pedestrian traffic as well.

Combined with the archaeological record we can reconstruct what seem to be some policies to ease congestion and keep a steady flow of traffic. Along many of the surviving Roman roads we find ruts worn into the stone that shows clear evidence of heavy traffic by carts and other vehicles. These are used to construct a more detailed understanding of how traffic worked in microcosm.

Pompeii gives us our best impression of how these regulations would have worked since almost the entire city streets are preserved and excavated, so we can develop a fuller picture in an urban setting. Studies of these roads reveal interesting morsels of information. For example near the Vicolo del Lupanare (the brothel street) you can still see a small area for parking carts, and ramps have been found across the city leading to stables and buildings that would have been used for parking and leaving animals – essentially ancient parking lots (Poehler, 2005). Interestingly the number of ramps in front of private housing is far lower, suggesting that wheeled transport was mainly used for commercial purposes such as transporting cargo (Tilburg 2011).

Some scholars, such as Tsujimura and Wallace-Hadrill (1991, and 1995, respectively) have used the ruts found in the streets of Pompeii to map the major thoroughfares and traffic routes, and the evidence suggests that the traffic flow was deliberately designed in zig-zags or parallel routes to avoid traffic building up, and a one-way street system since the streets were narrow and could not accommodate multiple vehicles. The Forum (and others elsewhere in the empire) seems to have been strictly off-limits to vehicles and were only used by pedestrians. Wider roads did of course exist in many other areas (even in some parts of Pompeii) and there is evidence that there was, as you asked, rules on driving on the “correct” side, though this appears to be localised rules. For example archaeological evidence of ruts worn into the roads near a quarry mine near Swindon, in the UK, suggest road-users drove on the left (coincidentally as we still do! Tilburg 2007), whereas some (Poehler 2005) believe drivers in Pompeii drove on the right where the wider roads allowed it.

There (as far as I’m aware) is no evidence of street signs or other such things that we use to direct traffic today. However in Pompeii there is some evidence that the ruts in the roads that can be seen have been manipulated by workers who dug them in certain ways to direct the flow of traffic (Tilburg, 2011). There are also stone barricades that can still be seen in parts of the city that blocked off vehicular traffic.

But who had right of way? And were there traffic violations similar to our own? As to rights of way we are unsure, but another very interesting feature at Pompeii (and this can be seen in other areas) are the very high pavements for pedestrian traffic. This would allow people to avoid stepping in the refuse and waste that inevitably would collect in the city. Equally inventive (and surprisingly modern) are the stepping-stone street crossings that can be seen in many areas directly over the roads. These again are high up allowing people to avoid the street floor, and again there is evidence for workers chiselling out extra ruts in the ground, here likely to avoid carts crashing into the jutting stones. In high traffic someone would have to lead the cart through the streets on foot, making sure that the street ahead was clear so as to not block the roads. I have looked but cannot for the life of me find this, so take this last comment with a pinch of salt, but I remember years ago coming across an article/documentary where someone (perhaps Mary Beard? If someone else happens to know that would be great) discussed how the roads in Pompeii are deliberately angled so that when it rains the water flows on a slight downward slope, naturally cleaning the refuse.

Things so far sound very orderly, and for the most part they likely were (or at least far more than we might first expect), but inevitably there were arseholes who flaunted the rules even in the ancient world. There is not a comprehensive account for the fines for traffic violations, but there is inscriptional evidence to attest that these existed. For example, in Urso, Spain, a decree (the Lex Coloniae Genetivae Juliae, CIL I 594) mentions that “no person shall have the boundary roads or cross roads blocked up” and that there was a 1,000 sesterces fine for being caught doing so.

So as you can see there were similar traffic problems, restrictions and solutions in the ancient world as there are today. Traffic was mainly for commercial purposes rather than private, and breaking the rules could get you fined just as today.

I guess the next time you are caught in a traffic jam you could perhaps see the funny side by realising people 2,000 years ago had the same mundane problems. And be careful of getting into fights over road-rage, because as Oedipus teaches us, they very well might be your long-lost father!

Hope this helps!

References/Further reading:

Poehler, E. (2005) “A re-examination of traffic in Pompeii’s Regio VI”, Pompeiana.org.

Tilburg, C. (2007) Traffic and Congestion in the Roman Empire. Routledge, London and New York – the book to read if you want to explore this further!

Tilburg, C. (2011) “Traffic policy and circulation in Roman cities”, Acta Classica.

Tsujimura, S. (1991) “Ruts in Pompeii: the traffic system in the Roman City”. Opuscula Pompeiana.

Wallace-Hadrill, A. (2005) “Public Honour and private shame: the urban texture of Pompeii”, Urban Society in Roman Italy, UCL Press, London.

Many Roman roads included ruts for carts, either as part of their design or simply as the wheels wore grooves into them over time. From the wear patterns in these ruts and the curbstones that lined the streets, it's possible to detect which way the carts generally went, and how many lanes of traffic the road usually carried.

Unfortunately, to do so requires both the survival of the original cobblestones - which are usually a very attractive resource for future generations - and the preservation of minute signs of wear within the wheel ruts. That's a very lucky coincidence that simply doesn't exist for the overwhelming majority of ancient sites.

Luckily, there is one site for which it does - famously, Pompeii was suddenly and catastrophically buried, wheel-ruts and all, in AD 79. Much of the work on this is down to Eric Poehler, though it was the Japanese scholar Sumiyo Tsujimura (thank you u/XenophonTheAthenian) who first made measurements of the wheel ruts to generate basic information like how much traffic used different roads.^(1)

Poehler found a spectrum of traffic-management methods, ranging from the fairly 'soft' such as wheel-ruts that turned corners in a particular direction, encouraging but not requiring traffic to follow them, to one-way systems and more 'hard' methods of controlling the flow of traffic, such as erecting blockages in the street that would not allow a cart through. Putting this all together, you can generate a map of Pompeii's traffic system that looks something like this - and shows a reasonably complicated system of traffic management, with arterial roads with two lanes of traffic, smaller, mostly one-way roads intersecting with them, and areas closed off completely or periodically to vehicular traffic.^(2)

On two-way streets, people drove on the right - not a major surprise if you know that the Romans, by the 1st century AD, were deeply superstitious about the left-hand side and used it as a byword for the perverse, uncomfortable and ill-omened (the link takes you to a discussion on the subject between myself and u/XenophonTheAthenian). This can be seen from the wear patterns on the curbstones - when the iron 'tyres' of a Roman cart-wheel struck a curbstone, they generated an asymmetric erosion pattern.^(3)

One thing that isn't totally clear is how the rules were made and enforced - one thing you don't see in Pompeii is any sort of signage to indicate which roads went in which direction. It is, however, clear that much of the 'highway code' was local. This is best shown by the fact that many of these key features, from the wheel ruts to the stepping-stones provided to allow pedestrians to cross often wet and filthy roads, depend on the gauge of the carts, or the distance between their wheels. These aren't standard even in the Bay of Naples - quite a few carts found in the villages around Pompeii would have been unable to use its wheel ruts and have had major trouble navigating some of the roads.

Scholars disagree on who exactly made the rules - we know that city governments, most notably in Rome, did pass laws to regulate what could go on the roads and when (so Julius Caesar's Lex Iulia Municipalis, copied by the southern Italian city of Heracleia, banned heavy ox-drawn goods vehicles from the city during daylight, except on certain permitted business), and some scholars like Poehler, Cornelis Van Tilburg and Nico Van Den Berg have extrapolated this and suggested that city officials created and maintained the traffic plan.^(4) Another school of thought emphasises the roles of local residents and the drivers themselves - Alan Kaiser argues that much of the 'street hierarchy' came from the impromptu roadblocks that property owners were perfectly entitled to create, and even Poehler agrees with him that cart drivers would have needed to know and pass on a considerable amount about the current situation in the town in order to be able to get around effectively.^(5)

A final thing to note is that the roads could be dangerous - clearances were very small (rarely more than 18 inches) and Poehler reckons that even the best drivers would have regularly hit the curb, which helps to explain the richness of his dataset. Roman case law was full of examples, real or hypothetical, where people were injured by wagons and mules. Moreover, even with pavements, there was very little separation of pedestrians and heavy traffic. Juvenal has a satirical poem about going out and about in Rome:

...another cart’s bearing a whole pine-tree.They teeter threateningly over the heads of those people below.Now, if that axle breaks under the weight of Ligurian marble,And spills an upturned mountain on top of the dense crowd,What will be left of the bodies? What limbs, what bones willSurvive? Every man’s corpse, wholly crushed, will vanish alongWith his soul.

And a tombstone in Ostia, which you can see here, preserved this episode:

To the Spirits of the Departed of Quintus Volusius Anthus, son of Spurius, of the tribe Lemonia.

As the little boy happened to play around, under the protection of a common parent, he fell down, due to the envy of fate. For a carter, with inexperienced yoked wild oxen, ran over by accident the unsuspecting boy, with the rim of his wheel.

All in all - yes, there were rules, but poor Laius was far from the only person for whom they didn't exactly work.

Notes and Sources

^(1) Poehler has collated his work in his 2017 book The Traffic Systems of Pompeii, which is the best starting point if you want to look into this subject further. Tsujimura's article is S. Tsujimura (1991) 'Ruts in Pompeii: The traffic system in the Roman City', Opuscula Pompeiana 2, pp58-86.

^(2) From Alan Kaiser's chapter, 'Cart Traffic Flow in Pompeii and Rome' in Ray Laurence and David Newsome's 2011 edited volume Rome, Ostia, Pompeii: Movement and Space.

^(3) Poehler explains the process in Traffic Systems and his 2006 article 'The Circulation of Traffic in Pompeii's Regio VI', Journal of Roman Archaeology 19, p58.

^(4) Van Tilburg and Van Den Berg in their paper 'A Tram in Pompeii' - I'm not sure if it's been published yet but it's available online. EDIT: This almost certainly was the law in Rome, but probably doesn't have anything to do with Julius Caesar: see here for more detail.

^(5) Alan Kaiser in his chapter above; Poehler in the interview he gave with the Archaeology, published as 'Rush Hour in Pompeii' in Archaeology Vol. 61, No. 6 (November/December 2008), p18.