HowTo/Scenery/mesh-table/directional
From TrainzOnline
directional
This tag is optional
Data type is a number i.e. 0
The default for coronas is to be aligned to the attachment point to face the NEGATIVE Z direction. This is especially useful for Traincars.
Adding this tag over-rides this behavior, to make the corona always face the screen – useful for scenery objects.
I am not sure as to what the "0" is meant to be but is suspect "0" (which I suspect means false) turns off the behavior. So do not use this tag if you want the default behavior to occur.