MACADAM ROADS.

Press, Volume LXIII, Issue 19150, 5 November 1927, Page 3

MACADAM ROADS.

A LIMITED CAPACITY* When traffie over a highway: is below 250 vehicles a day expenditure on a concrete road cannot be justified*, and a well-maintained macadam road.will give efficient service. The macadam road is named after the developer of this type of road in Great Britain, John L. McAdam, though, perhaps, it would be more fitting to name this style of road after the Trench provincial engineer, Tresaguet, who, about 150 years ago, began the building of improved highways as the term is understood to-day. McAdam's work in Great Britain began about 50 years later. At the time he was building roads in the North of England, Telford was building them in the South of England, and in Wales. The name Telford is still used to designate the type of foundation used by him. His plan was to take field stones, set them on end with the pointed edge up, and then break off points with a .sledge, and drive the pieces down as wedges to hold the stone firmlv. . ' ' i- . ■ ■

On" top of this was placed a layer of broken stone for a wearing surface. This type of foundation is still widely used in some parts where- the ground is low or marshy. McAdam's road was made of broken stone which the traffic would pack down. Bain washed the. smaller particles into interstices, and traffic would hold them there. Thus a smooth, even, hard surface would be produced. This method is practically identical with that of Tresaguet 50 years before. There are several types of macadam roads, each suitable for particular conditionst of traffic, foundation soils, and the availability of the materials for building them. In some coarse gravel or crushed rock is used for the base. Where the latter is used, particularly in country districts where rock suitable for road work is plentiful, a , crusher, is moved along, the road and the, rock; hauled to it from the adjoining fields*