by Greg Kotkowski

It is said that “all roads lead to Rome”. Is it true anymore? Certainly, during the Roman Empire main roads were constructed in such the way that everybody could easily reach the capital, the political and economical center of the country. Therefore if roads are built in order to facilitate the transportation toward the most important hubs, they could be used as an indicator of a region’s importance.

I downloaded the data of all contemporary roads in Italy from the OSM. As a starter, it is worth to plot them all (see Figure 1). It is interesting to see a sparse network of streets in the Alps and across the Appennine Mountains. Naturally, they are concentrated mostly in coastal areas and in valleys. It is also interesting to see the white spot at the location of the Etna volcano, while none is seen in correspondence of Vesuvius (people of Naples live under the risk due to the crowding of the area).

GKfig1
Fig 1. Map of all the Italian roads.

In fact, there is a printing shop in the USA that delivers on demand similar maps (more polished and in better resolution). It is possible to order a poster of Italy just for 60$. Well, I had not expected it to be such a good business.

Since in Figure 1 roads overlap due to low resolution, it is difficult to judge where the highest condensation is. It is rather easier to say which region definitely is not a heart of industry and economy. In order to plot the density of roads for given regions, we could use two-dimensional histograms where colors are related to intensities.

GKfig2
Fig 2. Histogram of road densities.

From Figure 2 it appears that definitely Rome still is an important hub, but also Milan and in general the Nothern part of Italy seems to be much more developed. In order to analyze this topic deeper let us plot a 3-dimensional  kernel estimation of roads density (Figure 3). As the data is geographical the resulting plot resembles the shape of Italy, however now the altitude of the peaks in the distribution corresponds to roads condensation.

GKfig3
Fig 3. 3D plot of roads density in Italy.

Although in Figure 3 the city of Rome generates a high and sharp peak, the regions of Venice and Milan create a broader highland and even what resembles a mountain range. So in the XXIth century it should rather be said that all roads lead to Milan.