13:36 Feb 3 

(albeit purely empirical!), the way FR uses these terms is somewhat skewed from the way they are used in EN, and hence the same term may not necessarily always be translated by the same term, depending on the exact nature of the object concerned.

For example, road bridges spanning river valleys in France are very often referred to as 'viaduc', even though I wouldn't have thought of them as an 'viaduct' in EN; and cf. the huge suspension bridge over the Tarn at Millau, which still gets called a 'viaduc'!

Some of the terms you mention seem to refer to a bridge specifically used to cross over something, whereas as we see from your source text, a 'flyover' may act as a bridge, but may also refer to an elevated section of road, i.e. not necessarily actually crossing anything!

You might do well to do a bit of research around the Paris Périphérique, as that has a number of elevated sections, and might help you find some related terms.