Traveling in a pre-industrial society is a common matter in role-playing games. When I design such games, I usually insert text and tables that show what distance it is possible to cover during a day, depending on terrain. They are based on my experiences or hiking, sailing and canoeing in the Swedish wilderness.
The Romans were the infra-structure experts of the Iron Age and their roads and bridges served as major conduits of trade and transport for centuries after the fall of the Western Empire. A game designer has a lot to learn from those people. Here is a link to a clever piece of software on that subject.