Intuitively, it seems to me that the world map should have roads and these roads should have some positive effects on speed.
However, even without roads, I can go from Werchag to Dhorak's Keep in a couple of days it seems. Or from Tihr to Tulga, no problemo.
When a merchant gives me a Rescue Hostage mission, I say "I'll be back in a flash" and voila! Three days later, here's your kid.
So, for me, the problem arises: Given that we're already moving fairly rapidly (and all the time, no rest for the wicked), do we need roads? If it increases our pace to where we can get on the Calradian Autobahn and go from Zendar to Halmar by lunchtime, are we better off gamewise?
I don't know. We might reduce travel speed offroad to half what it is now and make road speed equal to what it is now, in order to prevent a quick jaunt across the world in half a day.
And/or we could add:
*day/night travel: on roads travel day/night at higher rate than offroad.
*weather: if seasons were added, road travel could be less affected than offroad travel.
*spotting: using road makes one easier to spot, conversely not using the road reduces one's vulnerability
*tracking: using road makes one harder to track since traffic in either direction interferes with tracks along with a hard road surface.
Just some ideas, you all can come up with better.
What would prevent bandits, Dark Knights, etc. from using the roads exclusively? Maybe it could be coded that they not use them much - as if the roads were well-patrolled and dangerous for them.
Roads are an interesting idea. But I'm just a simple Zendarian street urchin and I'll leave the Highway Development to the transporation authorities in Khuldan.