§ Sir A. Meyer
asked the Secretary of State for Transport what is the average diameter, including centre grass verge, of overpass or underpass roundabouts used for interchanges on newly built dual carriageway roads; what acreage of land is required for such roundabouts; and what is the average cost of such roundabouts.
§ Mr. Horam
Each roundabout has to be designed to suit the circumstances and layout which apply at individual sites, and dimensions can vary widely. The typical layout upon which individual designs involving all-purpose dual two-lane carriageway roads is based is not circular, but this typical layout including a grass verge around the outside of the roundabout would be encompassed by a rectangle 115 metres by 130 metres. Such interchanges normally take about two or two and a half hectares of land more than that occupied by the dual carriageway all-purpose road and the road crossing it.257W
The costs of such interchanges vary considerably with subsoil, topographical and other conditions and are not readily available. Connecting a single-carriageway minor road to a dual two-lane carriageway all-purpose road in this manner, however might normally be in the cost range £0.6 million to £1 million at 1977 prices.