So I've been playing a lot of Civ 5 lately, and it occurred to me to drag up the idea of Terrain impacting movement, again.
I think it would make things far more immersive, interesting, and dynamic, if things like hills, mountains, forests, jungles, and so on, impacted movement speed, and/or if roads allowed for slightly faster travel.
This has been mentioned in the past, but I have a suggestion that makes it somewhat better than simply granting or penalizing moves (although this could be part of it).
The core concept is adjusting the "hasty" timer based on the terrain modifiers of the room you enter. Thus, you can still only move twice at a time, but you'd be able to move sooner on a road, or significantly slower, through jungle or mountains, etc.
Suggestion: ("movement time" is the amount of time until you can move again without getting the "hasty message")
Roads: -25% movement time, and ignore forest, desert, and water terrain modifiers.
Forest: +20% movement time
Jungle: +33% (halved if a road is built)
Mountains: +50% (halved if a road is built). Alternatively, have movement through mountains/jungles expend movement (like Dash) unless on a road.
A config option could be easily added to show when this delay takes place (which would help significantly in adjusting mapper/autowalking routes).
This would make construction/maintenance of roads far more interesting and important, and would make travel and combat far more immersive and dynamic. The system would also be pretty simple to implement, albeit would require some minor adjustments to the game engine's movement timer system.