What is the definition of an inter-change in Tanzania ?? because, in civil engineering --
an interchange is a road junction that uses grade separation, and typically one or more ramps, to permit traffic on at least one highway to pass through the junction without interruption from any other crossing traffic stream.
next to the term grade separation,
A grade separator is a general term.
A flyover is a special case and an example of a grade separator.
Flyover is a popular term used by the public.
Grade separator is a technical term used by Engineers.
Grade separators in general are arrangements where traffic from various directions crossing at a junction are allowed to cross each other at different heights.
Grade separators can include flyovers, (or over-passes), underpasses, tunnels, road or rail bridges. The term is used to differentiate it from a level crossing or traffic intersection with signals, roundabouts, diamond crossings etc.
All flyovers are grade separators. All grade separators are not necessarily flyovers.
I hope this is clear.