From the names of successive Emperors on milestones of the same road, archaeologists have calculated that the average life of a highway was thirty to forty years. Two points should be emphasized: first, this represents an ideal method of construction, not often exemplified in practice; second, to a modern engineer a road like this would seem insufficiently elastic, a five-foot wall in the flat, too rigid for the stresses and strains to which it was subjected. Hence perhaps the frequent need for repairs, but Roman traffic was lighter than ours, and the very fact that we can write about the roads at all is a tribute to their durability. Upon roads like these, under the Empire, travelled the Imperial posting service, with relays of messengers, and post-houses where horses and carriages could be changed. Under exceptional conditions the Emperor Tiberius, using this service, once travelled 180 miles in a day, a rate of speed not equalled on European roads until the nineteenth century. The next major road laid out after the Appia must have been the Valeria, which was needed for eastward communication via Tivoli with the new colony of Alba Fucens, founded, as we saw, in 303 B.C. Archaeology has shown that in general the foundation of a colony precedes the laying down of the metalled military road. This is true of Cosa (foundation date of the colony, 273 B.C.; probable date of the Via Aurelia which served it, about 241); of Ariminum (founded 268 B.C.; reached by the Via Flaminia in 220), and of the Roman colonies in the Po valley; _e.g._, Bononia (Bologna: founded 189 B.C.; reached by the Via Aemilia after 187). The full extension of the Via Valeria beyond Alba to the Adriatic had to await the pacification of the Samnite tribes of central Italy and the granting of citizenship to Italians after the “Social” War, in 89 B.C. Milestones on this last stretch belong to Claudius’ reign (A.D. 41–54).