Code Query - Underground ducts (RGS-metallic)

[cherryg222]

We know that for underground ducts (in concrete), with arrangement as per Fig.310.60(C)(3), with MV cables, we use the Tables 310.60(C)(77)till (80).However, as detailed in Handbook, the term "electrical ducts" refers to nonmetallic conduits. Does this mean these tables pertain to non-metallic conduits in duct bank only? Which tables need to be followed for RGS conduits in concrete duct bank? The query is pertaining to NEC 2017 and Art.310.60.