Hi David
Can't remember if I've seen this a somewhere else, maybe Face book but....
It's a mix of 4.2.1 movement rates and passage of lines.
Passage of lines - you loose movement like you were going through rough terrain, ie you pay double the distance.
But do irregulars and lights count this as a level better is no loss of movement.
And do artillery count it as a level worse is as dense terrain.
I am assuming the answer to both is no, especially for artillery cos they would have to halt upon entering and be stuck on top of the other unit which is expressly prohibited in the rules.
Thanks in advance
Steve Nutt
The intention was that neither of these would impact passage-of-lines, i.e. passage-of-lines always simply costs double the movement for the distance the Unit moves through.
-David