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Page:Popular Science Monthly Volume 80.djvu/330

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326
THE POPULAR SCIENCE MONTHLY

SCIENCE IN THE SERVICE OF HIGHWAY CONSTRUCTION
By CLIFFORD RICHARDSON, M.Am.Soc.C.E.

NEW YORK CITY

IN a popular sense, a road is a means of communication by vehicle between different localities. To the citizen who ordinarily uses it, aside from considerations of its aspect and surroundings, the condition of the surface and the ease of traction over it have been the main considerations. He has given little thought to the manner in which it has been constructed and has been, usually, quite indifferent to or ignorant of its cost originally or of that for its maintenance. As the use of the automobile has become so general there has recently been a very decided change in this respect. The movement for good roads has arisen and a general interest in the subject has developed. In what follows an attempt will be made, for the benefit of the general reader, to outline the development of the modern methods of highway construction, and to show how science has aided therein.

The art of highway engineering, that is to say, of the construction of roads, was considered to have been developed to a high degree of perfection at the end of the last century, as evidenced by the magnificent system of broken-stone roads which were in existence at that time in France, more especially, and in England and other foreign countries, while in the United States successful systems of broken-stone roads had been begun in New Jersey, Massachusetts, Connecticut and a few other eastern states. Roads of this type, when constructed by engineers of experience, with suitable stone, of a proper thickness and with a sufficient foundation, properly drained, and when continuously maintained, were found to be adequate to support the severest kind of travel to which they were subjected at that time, at a cost which was not an excessive burden on the state or the taxpayer. The traffic consisted almost entirely of horse-drawn vehicles and the road surface was resistant to a degree which would carry this traffic without rapid deterioration. Roads of this character were known as water-bound macadam, a name derived from their resemblance to the broken stone roads constructed in England by the celebrated highway engineer John Loudon Macadam in the early part of the last century. Briefly, water-bound broken-stone roads, of the highest type known in the United States, and the only form built until recently to carry heavy travel, are constructed as follows: