example:
at Altis grid 092191
all stone with this kind of color or texture cant be walked on,
if you fall onto it, player will be stuck in a "falling" or "jumping" animation,
vehicle can drive on it just fine.
example:
find dark grey stone at Altis grid 092191,
walk on it
cant
half drive on it
exit vehicle
you fall on it
player stuck in a "falling" or "jumping" animation