Wouldn't "segregated" be physically separate, eg. on the pavement or with kerbs between the lane and the carriageway, whereas "mandatory" would be physically on the road but with a solid white "do not cross" line?
The switching sides thing that happens on CS3 (East of that area) is totes bonkers.
I don't see how ^^^ that definition of "mandatory" stacks up against "segregated", which is also used in the document.
Maybe a mandatory one is against the flow of the main carriageway on a one way section?