I guess a hex map with 12 miles per hex would work. This would allow 2 hexes walking on a road or just one in rough terrain, or even half of one in a swamp. This would also work fine with 6 miles or even 4.
Again, forget these stupid "miles". There are no miles, thats not needed you making it more complicated by trying to add in distance.
You just have hex fields in different colours. Depending on the colour they have time value 1, some 2 some 3 some 4, some 5 some 6.
Like normal travel rout is 2, perfect road is 1, grass is 3, forest is 4, sand is 5, swamp is 6, mountain is 7 etc.
Traveling a hex takes time units time. No need for any artificial distance like "miles" 2 villages are 4 time units away from each other etc.







