He distinguished a first layer, one meter thick, of earth and gravel, originating from the neighboring mountain region, its width defined along the edges by two lines of large stones. On top of this was a thinner layer of gravel and crushed limestone, its width likewise defined by two rows of large stones, this time closer together. On top of this can be seen several layers of resurfacing of the same type. He also notes a place on the via Aurelia near Civitavecchia where the first layer was made of compacted tufa 40 centimeters thick. Such data illustrates the three distinct layers and also demonstrates the different materials used depending on what the land in the road s immediate vicinity offered during construction.
Intentional ruts are an interesting feature of some ancient Roman roads.
While there are some ruts that developed from general use, there are others that are purposeful, between 6 and 30 centimeters deep, with sharp edges shaped by a pick or a point and hammer. Adam says that the ruts would give the impression of the standardization of the distance between wagon wheels. In general, we may assume, the wider the road, the greater its importance. Margary lists all the travelers that used the roads, among them military leaders and their forces, high dignitaries, merchants traveling on business, and sick people seeking treatment, to name a few. The list continues for nearly a page, indicating the amount of traffic the main roads carried and why such width was necessary.