It’s easy to understand that in the Middle Ages the road to Pisa was travelled by pilgrims when you see all the hospices lining the route, even at the very beginning, near Porta San Frediano in Florence.
There were often accommodations next to these shelters, the number of which skyrocketed in the larger cities, particularly in Empoli and Lastra a Signa.
The medieval route of the via Pisana more or less replicated the Roman road to Pisa, the via Quinctia. Because of flooding and changes in the flow of the Arno, there’s no longer any trace of the Roman road. The modern road follows the direction of the medieval route to Pisa, those it’s likely that the latter stuck more to the foot of the hills, running along the Arno’s course.
The succession of small towns, many of which are characterized by the typical elongated form of “street villages,” leave no doubt about the significant overlapping between the modern road and its medieval counterpart, which in the 1800s was highly travelled.