Hiya! I'd like to see your campaign when you're done!
There are two places where you can set the movement penalty for terrain. There is the Movement Class (rough, open, elevation, etc) and then the terrain that you create (suburban, plains, river, etc). Both of these have modifiers.
The Movement Class has a varying modifier depending on the movement type of the unit traversing that terrain. The movement class modifier can be changed from 0 to 90% (and is accessable from the "Edit -> Movement Charts" menu.
The terrain modifier (accessable from the Feature Picker button "Edit", or when creating a new terrain feature) allows any value from 0 to 100 (the up/down arrows jump by 10, but you can type in any value you'd like).
There are two types of roads which give movement bonuses in Campaigner. If you want better control over movement, you can forgoe using the FlexMap roads, and make a terrain feature of your own to represent roads.
Here's how I would do it (without using the FlexMap roads):
Make a Autobahn terrain feature, using the "Open" movement class with its own movement modifier of 0.
Make a Highway terrain feature, using "Open" movement class with its own movement modifier of 15% (or whatever feels right).
All other terrain features: urban, forest, etc, should have a steeper penalty for movement.
Then, you'll have to tailor your movement speeds in Campaigner to take in consideration the fastest movement possible as the default. (so, instead of 5 movement points, you'd say the unit has 15 movement points - which it would get but only on the Autobahn).
Hope that made sense! If not, let me know, and I'll try again
