By Tim Angelos
All Photos by author unless otherwise stated.

Introduction

For over two thousand years it has been said that all roads lead to Rome. In fact, Rome is home to some of the first permanent roads ever built. The city itself has been continuously inhabited throughout this time, from before the Roman Empire into modern times. To say the city has been and is important is an understatement. Including being the capital of a massive empire to being the capital of Italy and an invaluable site for the discovery of human history. During this time the city has been tied to the rest of the world by the road. In modern Rome the road becomes complicated and intertwined with history, tourists and modern transportation.

This paper attempts to highlight and analyze the road as it is in modern city of Rome. The focus will be on the use of different pavement types, specifically cobble stones, known as sanpietrini, and asphalt concrete pavements. It also discusses the impact of the different types, the impact and effective use of each. This will be presented through observations supplemented by additional academic research.

History: Roman Roads Over Time

Beginning to understand how the road developed in the eternal city we must begin in the early days of its inhabitance. The first road leading into the city of Rome was constructed in 312 BCE. This was the Via Appia (Appian Way) and it was constructed out of stone and concrete stretching initially for 196 km (Cartwright). These roads followed a set of standards for how a road should be built that was laid out in the Laws of the Twelve Tables. The implementation of the Roman road network allowed the capital city to expand, trade goods, move military and stay connected with its growing empire.

The next major step for the road in Rome was the beginning of the use of a small paving stone with a square shaped surface that became known as the sanpietrino. This was especially important for the roads in the central areas of the city and continues to influence the city’s roads today. First used in the 1500s by Pope Pius V, where they were used to pave Piazza San Pietro. This is where the name sanpietrino comes from, roughly translating to “little St. Peters”. Soon much of Rome’s streets and Piazzas were paved with the material and at the time it offered a smoother and more reliable surface for carriages (Zoccali).    

In more recent times Rome has tried to keep pace with the rest of the developing world. Highways for cars were built connecting the city to the rest of Italy and Europe. Rome’s Grande Raccordo Anulare, the city’s ring road, was completed in 1970. Along with advances to modern roadway systems began the use of asphalt concrete pavement in the city. By the late 1800’s asphalt was becoming more popular as a roadway material around the world.

In Rome today, along the streets of the city center a mix of pavement types and methods can be observed. Much of the city streets are still paved using the traditional sanpietrini, however more and more asphalt is taking over. Many high traffic areas have gotten an often-crude overlay of asphalt right over the sanpietrini. While on other streets the stones are becoming lose from constant vehicle traffic or being filled with cement or asphalt.

Roadway Construction and Design

i.  Construction Materials

The original sanpietrino of the 18^th century consisted of basalt stone from the Alban hills and measured 9.5cm wide by 18cm tall side view with a roughly square top surface (Cosentino). They are typically the shape of a truncated pyramid as shown in figure x below. They can range from a 6 x 6cm to a 12 x 12 cm surface. These basalt stones are cut by hand from the numerous quarries on the outskirts of Rome. Basalt is a particularly hard material and therefore can last for a very long time, making this paving method very long lasting, assuming the stones stay in place (Mohora).

Hot mix asphalt (HMA) is the other main pavement type found covering the city streets of Rome. According the Pavement Interactive HMA consists of two main components, aggregate and asphalt binder. Further information on this pavement type, the materials associated with it and common practices can be found by following the link. 

For both pavements a base course is typically required which consisted of compacted aggregate leveled and graded to specification. This material creates a barrier between the surface course and the subgrade in both cases. In the case of sanpietrini there is an additional material needed to complete the process. That is the addition of a bedding course. This material is typically a sand like material that can fill the gaps. When this is used it allows some water to permeate the surface course reducing surface run-off. It is important to note that in recent years asphalt and cement filler have been used to fill the gaps between the sanpietrini in many areas of the city.

ii. Pavement Uses and Vehicle Types

Various areas of the city are used in different ways by different users and therefore require additional considerations. The first user is the pedestrian. From observation many piazza areas, especially in the historical district of Rome, tend towards being mainly utilized by the pedestrian. This includes many of the roads through the Trastevere neighborhood and similar places as well. In these areas the needs of the user when it comes to pavement are a reduced risk of flooding, feeling the historic charm of the city and having a safe place to walk free of degradation due to vehicle traffic.

Another user to consider is traffic and heavy vehicles. Although the historical areas and the city center of Rome have restricted driving zones, there are still many streets throughout the city that carry a high volume of daily traffic. These areas need a pavement that is quiet, offers traction, and that can support vehicles with greater loading on the road without extreme degradation of the roadway surface.

Rome sees a wide variety of vehicle types on its inner-city roadways. There are some brave cyclists who struggle to navigate potholes along the bumpy cobblestone streets. There are those who drive mopeds or motorcycles as well as the daily automobile traffic. The city must also operate garbage, tram and bus services on these streets. 

Table 1. Comparison of users and needs

iii. Methods

Both full depth asphalt paving and paving with sanpietrini involve similar basic layer of different courses of material. From bottom up they are laid on a subgrade, then a base course is placed followed by the surface course. Sanpietrini will have the gaps filled with a bedding course to hold the stones in place. According to Mohora the cost of paving with sanpietrini is significantly higher than paving with asphalt but requires less maintenance aside from occasional cleaning. This might explain why it is common in some areas of Rome to see utility work that was completed underneath a sanpietrini street to be filled back and surfaced with asphalt. As shown in the graphic below this method requires the stones be contained by an edge restraint such as a curb or gutter. In Rome these are typically white travertine blocks cut with interlocking joints.

Although many of the highways and newer high-volume roadways surrounding Rome are designed and constructed using full depth asphalt, from observation it is much more common in the city center for high-volume and high-speed roads to have an asphalt overlay on top of the sanpietrini. In this situation a wearing course of asphalt a few centimeters thick is placed over the existing roadway and finished with a smooth surface. When this is done it is easily seen in Rome because the surface cracking on the top of the asphalt begins to show the shape of the sanpietrini as shown below. This is like when a cement concrete road gets paved with an overlay in the United States. The flexible asphalt pavement cracks where the expansion joint between concrete slabs was on the underlying pavement.

Impact

i. Perception

In Rome and many of Europe’s historical cities the cobble stone gives the impression of history. It helps create the atmosphere that is unique to these rich historical cities. Standing on top of asphalt while looking up at the colosseum just isn’t the same as standing on the older paving method associated with cobble stone and the sanpietrini. For tourists it has become part of the attraction of Rome. Modern cities without deep historical ties are generally paved with uniform concrete cement or asphalt concrete pavement. In Rome one finds both uniformity and non-uniformity in the pavements in the city center. This is for two reasons. The first is intentional, the sanpietrini, each stone is roughly cut the same, but each looks unique at the same time. They are then placed in patterns along the area to be paved. The second appears unintentional, the overlays, many of which are cracked incomplete and showing the stones underneath.

The sanpietrini also presents another problem, noise. For residents of the city they are loud and difficult to navigate for many users. For example, riding the city’s ATAC buses, every time the bus encounters this pavement it rattles loudly and some of the buses feel like they are about the fall apart. This is not good for the longevity of Rome’s transit network. Heavy vehicles like busses on these streets also create vibrations through the sanpietrini that have a damaging effect on the city’s architecture. Sanpietrini also make the city unfriendly for cyclists due to the bumpy ride along with the narrow streets and impatient drivers.ImageDrag an image, upload a new one or select a file from your library.UploadMedia LibraryInsert from URL

ii. Issues with Repair Methods

Repairing the paving stones and working beneath them also comes with great challenges for the city. Cutting and placing the paving stones is specialized work. In fact, according to the NBC article there were only eight masons remaining as of 2005 that know how to properly hammer in the stones. Therefore, this paving method can be costly and time consuming compared to other methods. The result is poorly done patch jobs following construction activities such as utility work. This solution is unappealing and ruins the charming effect the stones have on the city.

The traditional procedure for this paving method is to use a bedding course of a material like sand. However, with heavy traffic the stone tend to come loose creating potholes and uneven pavement. To combat this, the solution in Rome is to fill the gaps with either asphalt or cement. When this is done it effects drainage, without the sand bedding water does not drain. The sand bedding allows small gaps to remain between the stones where water can pass through (Zoccali). Without the sand the pavement goes from being permeable to being impermeable. Architect Tom Rankin demonstrated this effect by pointing out the example of a tree in Piazza della Quercia. The gaps between the stones had been filled with cement at one point, shortly after the tree in the center of the piazza died. This demonstrated how the drainage properties of the pavement changed with a different fill material.

Conclusion and Paving the Future of Rome

The image of the city of Rome is tightly intertwined with the cobble stone pavement known as sanpietrini. Being a city with an identity closely tied to its rich history is part of this effect. A history that includes the first permanent roadways. In the modern city the roads are a mix of the famous sanpietrini, and roads paved with hot mix asphalt. Modern vehicles pound the cobble stones which in turn rattle busses and become slick in wet weather. Each of the two methods employed by the city today have a place in the modern capital city. According to X article Rome has begun to understand where this is. High traffic volume and speed areas need to tend towards asphalt surfacing, while low volume areas and areas reserved for mainly pedestrian traffic can and should be paved with sanpietrini. Currently this is often done using asphalt overlays which cover some areas of the cobble stones. These overlays show the hidden paving stones they cover either in places where entire sections have been worn away or through cracks that reflect the divisions between the stones.

There are numerous possibilities for the future of roadway construction within Rome’s city center. For one, many benefits can come from replacing high traffic cobblestone areas with full depth asphalt. The pavement will be longer lasting than adding a thin overlay on top of the stones. When this is done the stones can be removed and used to replace stones in other areas of the city. This removes the need for the specialized stone cutters who are all but extinct. Rome must also attempt to preserve the charm of its sanpietrini streets and piazzas by patching cobble stone with cobble stone rather than asphalt. They also need to consider the differences between permeable and impermeable pavements and construct (or not construct) drainage as necessary. If these considerations are taken, Rome can preserve its charm while accommodating modern transportation.

Works Cited

Mohora, Irina, and Anamaria Andreea Anghel. “Urban Landscape- Cubic Stone Streets in Historical Areas, Advantages and Disadvantages, Case Study Timisoara Versus Rome.” IOP Conference Series: Materials Science and Engineering, vol. 471, 2019, p. 082028., doi:10.1088/1757-899x/471/8/082028.

Zoccali, Pablo, et al. “Sampietrini Stone Pavements: Distress Analysis Using Pavement Condition Index Method.” Applied Sciences, vol. 7, no. 7, 2017, p. 669., doi:10.3390/app7070669.

Cartwright, Mark. “Roman Roads.” Ancient History Encyclopedia, Ancient History Encyclopedia, 24 Sept. 2019, https://www.ancient.eu/article/758/roman-roads/.

“Rome Trading Cobblestone Streets for Asphalt.” NBCNews.com, NBCUniversal News Group, 25 July 2005, http://www.nbcnews.com/id/8700967/ns/world_news-europe/t/rome-trading-cobblestone-streets-asphalt/#.XYsBJJNKhPZ. Paragraph

Cosentino, Gianluca. Stone Road Pavements. MS Thesis. Sapienza University of Rome, 2017. https://web.uniroma1.it/cdaingtrasporti/sites/default/files/Thesis_GianlucaCosentino.pdf 9/24/2019.

“Pavement Interactive.” Pavement Interactive, https://www.pavementinteractive.org/.

“Traveler’s Guide to ZTL Driving Zones in Italy.” Auto Europe, https://www.autoeurope.com/italy-ztl-zones/.