ABSTRACT
In the Roman and Han Empires there were no important innovations in transport vehicles, but the rulers did construct large-scale land transportation systems. They built great networks of roads, tunnels, bridges, and canals over which official couriers passed. The period from 200 BC to AD 200 is notable in that favorable climate and population growth made possible two empires of about fifty million people each. These were the largest integrated political units ever seen on earth until that time. In the period AD 250-500 cold weather and population decline contributed to political disintegration. In the fifth century AD nomad steppe barbarians consumed the remains of the Roman and Han Empires. Then for five centuries population failed to grow, and power remained fragmented. In the Mediterranean world the Roman era was not a time of major technological innovation. The Mediterranean peoples used crops and methods that had proven successful in certain areas and extended them to others.
