HPS Sim modern Campaign ?

[Apollo11]

When unit is "on foot" it can move into marshes for example.
"On foot" mean that this unit leaves his vehicles and move without transport and use only foot movement cost.
All motorized or mechanized units have two types of movement: foot and type of they own vehicles, and this kind of unit can not move into hex that is impassable at least for one of type of movement, even not in travel mode
You can found table of movement in parameter data dialog