MacAdam

John MacAdam was born in Ayr on September 21, 1756. In 1783. MacAdam started experimenting with a new method of road construction. When he was appointed surveyor to the Bristol Turnpike Trust in 1816 he remade the roads under his control with crushed stone bound with gravel on a firm base of large stones. A camber, making the road slightly convex, ensured the rainwater rapidly drained off the road and did not penetrate the foundations. This way of building roads later became known as the Macadamized system.

As a result of his success, MacAdam was made surveyor-general of metropolitan roads in England. By the end of the 19th century, most of the main roads in Europe were built in this way.

Modern road surfaces are still largely dependent on MacAdam's discovery. Coal tar was first used to bind the stones together, hot-laid tarred aggregate or tar-sprayed chips providing an excellent road-metalling for the surface. Oil-based asphalt from Trinidad and from refineries was later used as a road surfacing, laid on reinforced concrete, but still owes a lot to MacAdam as it is mixed with granite or limestone chippings. This process became known as Tarmacadam (a short form of which is used to refer to airplane runways: "tarmac").