Code:
[Clear]
Foot=10%
[Rough]
Foot=10%
[Road]
Foot=100%
In theory, this should slow down infantry CONSIDERABLY when moving on clear or rough terrain, while infantry moving on areas of pavement will move at full speed.
The attachment shows the results of the test.
By the way, pd, Float is definately a typo. Infantry do indeed default to SpeedType=Foot.