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Macadam is a type of Road Construction pioneered by the Scotsman John Loudon McAdam in the early 1800s . It consisted of creating three layers of stones laid on a sloped Subgrade with side ditches for drainage. The first two layers consisted of angular hand-broken Aggregate , maximum size 3 Inch es (75 Mm ), to a total depth of about 8 inches (200 mm). The third layer was about 2 inches (50 mm) thick with a maximum aggregate size of 1 inch (25 mm). The layers would be compacted with a heavy Roller , causing the angular stones to lock together with their neighbours.

This basic method of construction is sometimes known as "water-bound macadam". Although this method required a great deal of manual labor, it resulted in a strong and free-draining pavement. Roads constructed in this manner were described as "macadamized".

With the advent of - can still be sometimes found in New England.-->