Vol. 436 No. 4
53 Mr. McCormack asked the Minister for the Environment the reason 12 to 14 inches of tarmacadam is now being used for the repair and surface dressing of national primary routes; and if he will make a statement on the matter.
The normal thickness of the layer of bitumen and stone chippings used in the process of surface dressing is 12mm (½ inch). In the case of pavement improvement works, where an existing road is being strengthened and reshaped to modern design requirements, the layers of materials used would generally involve a minimum depth of 200mm (8 inches). The thickness and type of each layer could vary from one project to another, depending on factors such as traffic volumes, proportion of heavy goods vehicles, and soil type underlying the road.
