[PatG]

I think I've got it - or 75% of it anyway.

To refine my post above:

1) If supported by the code, take the existing tramway and rail terrains and make them passable by unit class 0 - Fortifications.

2) Make all other terrain impassable by unit class 0.

3) Base all trains on class 0 base units. The user will assign a move as required.

Units can be placed on terrain they cannot move through.

Since all AI usable class 0 units have move 0, there will not be any problems with unit placement or trains sailing up the river.

remaining problems:
1) controlling heading.
2) keeping trains together as units.
3) sound is not the best but I can live with it.

Any comments?