An expressway above Orrong Road is one of two options that have been identified to fulfil former transport minister Troy Buswell's dream of a non-stop road route between the city and Perth Airport.
The viaduct, which would cost many millions of dollars, would be the first of its kind in WA.
However, viaducts are widely used in other parts of the world, particularly in Europe.
As reported by _The West Australian _ in June 2011, Mr Buswell asked Main Roads engineers to examine the feasibility of an expressway from Graham Farmer Freeway to Leach Highway with no intersections and no traffic lights. He said at the time it could be built above, under or next to existing roads.
This week Main Roads revealed it had completed a study into the feasibility of upgrading the 4.2km section of Orrong Road between Great Eastern Highway and Leach Highway and identified two options - an elevatedexpressway or viaduct, or a six-lane expressway with limited interchanges or traffic lights.
A Main Roads spokesman said the expressway was "a long-term project".