Remarks on the Present System of Road Making: With Observations, Deduced from Practice and Experience, With a View to a Revision of the Existing Laws, and the Introduction of Improvement in the Method of Making, Repairing, and Preserving Roads, and Defending the Road Funds from Misapplication. Seventh Edition, Carefully Revised, With an Appendix, and Report from the Select Committee of the House of Commons, June 1823, with Extracts from the EvidenceMcAdam, John Loudon
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Remarks on the Present System of Road Making: With Observations, Deduced from Practice and Experience, With a View to a Revision of the Existing Laws, and the Introduction of Improvement in the Method of Making, Repairing, and Preserving Roads, and Defending the Road Funds from Misapplication. Seventh Edition, Carefully Revised, With an Appendix, and Report from the Select Committee of the House of Commons, June 1823, with Extracts from the Evidence
McAdam, John Loudon
Macadam roads; Roads -- Great Britain
The disadvantages of a flat road again are, that even if it is supposed
to continue so, it is bad in principle, by doing away the tendency which
a road ought to have, in every direction, to clear itself of water; but
as the greatest wear will always be in the middle of the road, a level
or flat road will very soon be concave; the middle of the road then
becomes the watercourse, and the consequence, if the road is upon level
ground, is, that the water and mud lie upon it, and injure the
foundation and materials; or, if otherwise, that the stones or materials
of the road are washed bare, and liable to be loosened and thrown up by
the wheels coming into contact with their exposed angular surfaces. Many
of the roads in the country afford examples of this, particularly after
heavy rains, and if the country is at all hilly.
The best form for a road, in order to avoid those evils, is,—in my
opinion, to form it, and to keep it with just a sufficient rise towards
the middle, to incline the water towards the sides; and in place of
making the whole width the section of one curve, to form it by two
straight lines, forming inclined planes, and joined by a curve towards
the middle. I have prepared a section of a road in the manner I have
described (No. 4.) and as the lines, excepting at the centre, are
straight, the section may be made to suit almost any greater or less
width, by merely extending them. The section is taken nearly from a part
of a road made under my direction in the country. The dotted line drawn
upon it shows the form I alluded to when speaking of the circular road
that ought to be avoided. I have seen ridges formed in what I thought
well formed land, much after what I would recommend for the form of a
road. The object of forming the land into ridges, raised a little in the
middle, is the same as that of raising the middle of a road to prevent
the water from settling upon it, and what is sufficient for the ploughed
land is certainly enough for a road. If the road is of good stone, four
to five inches rise in ten feet is sufficient, gravel, and other
inferior material, will allow a little more. In this section it may be
worth while to notice the situation of the hedge and ditch, or rill on
each side of the road, a more common, but I think a more dangerous and
worse way, is to form the ditch close to the road, and to plant the
quick upon a raised bank beyond it. I have dotted this mode also upon
the section. The advantage of having the hedge next the road, consists
in its greater safety to the traveller, particularly if a ditch of any
considerable depth is necessary, and in the hedge being supported in its
growth from the ground under the road, without drawing upon the farmer’s
side of the ditch; and it is I believe, this last advantage, which has
led the author of an article in the Edinburgh Farmer’s Magazine, with
whom I am acquainted, to make nearly the same observations. In a length
Public-domain text, read in full here on John Shaqi.
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