At the height of the empire, some 300,000 kilometers of graveled or paved highways linked the disparate provinces to Rome (Forbes 1955: 138). The width and quality of these roads varied tremendously. The majority of routes were simply graveled paths.
Under dry conditions, these were perfectly adequate, but in poor weather they might turn into ‘‘deep impassable mud’’ (Procop, Aed. 5. 3. 12-13). Routes such as these have not withstood the passage of time. What remains today are stretches of premier roadway, the result of skilled engineering and considerable monetary outlay.
First a bed was dug and leveled. On all but the flattest terrain, absolute straightness was abandoned in favor of following the contours of the land. In rugged terrain, routes usually followed older paths, skirting mountains and avoiding defiles. But, if the need were great enough, Roman engineers were prepared to bore through mountains or cantilever a roadway along the side of a cliff (Forbes 1955: 150; Chevallier 1976: 104-6). Even when tunneling through solid rock, military routes had to be at least 8 feet wide to accommodate heavy baggage wagons. But the most typical road width was 10 Roman feet, a span only slightly narrower than a modern lane (Casson 1988: 354).
Once the roadbed was prepared, it was filled with a foundation mixture of broken pottery, small stones, and usually some waterproofing material. Heavy rollers were used to flatten this mixture to prevent heaving and cracking. Finally, flat paving stones were fitted closely together to form an unbroken surface (Forbes 1955: 146-7; Casson 1988: 354). The surface was slightly crowned and ditches were dug on either side to facilitate drainage. The result of this labor was a road some 100 to 140 centimeters (39-55 inches) deep, or three to four times the depth of a modern roadbed (Forbes 1955: 148). Roads built over unstable ground might require even more elaborate construction techniques (Chevallier 1976: 89-90).
This impressive technology gave Roman roads exceptional durability: they could sustain the wear of iron wheels for seventy to a hundred years before needing thorough reconstruction, though high-traffic stretches might need servicing every thirty to forty years. Even relatively simple cobble roads, in which cobbles were embedded in a 10-centimeter (3.9 inch) sand bed, probably had a life of ten to fifteen years (Forbes 1955: 148-9). In the northern parts of the empire, however, where frost caused cracks and potholes, roads needed more frequent repair. Funding for road works was initially raised through direct taxation, though private benefaction also played a role. Within Italy, the maintenance of the road system gradually devolved upon specially appointed officials; in the provinces it remained a duty of the governor (Ramsay 1904: 392).
World History
