OK, this idea was posted by Almightyjosh but i am gonna shed some light on it and make it better. Since there is some kind of travel between cities, how about having a set amount of time it takes to go from one square to another.
Like for now the time would be:
Really, Really fast horse: 7½ minutes per square
Really Fast Horse: 15 minutes per square
Fast Horse: 30 minutes per square
Semi Fast Horse: 45 minutes per square
Normal Horse: 1 hour per square
pack animal (Donkey, pack horse): 1½ hours per square
Walking: 2 hours per square
Now if ther is a road to the city, divide the times by 2, and if railroad, it takes 2 minutes per square.
Attacked:
Also because of the barbarians there could be a 50% chance to get attacked.
the more people with you the lower the percentage.
Say i am walking from bavaria to guganan, and it takes me 10 hours, i have a 50% chance of being attacked.
the attacking needs to be worked out, but the top part is definite.