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

by John Loudon McAdam

The fences themselves on each side form a very material and important subject, with regard to the perfection of roads; they should in no instance be more than five feet in height above the centre of the road, and all trees which stand within twenty yards from the centre of it ought to be removed. I am sure that twenty per cent. of the expense of improving and repairing roads is incurred by the improper state of the fences and trees along the sides of it, on the sunny side more particularly; this must be evident to any person who will notice the state of a road which is much shaded by high fences and trees, compared to the other parts of the road which are exposed to the sun and air. My observations, with regard to fences and trees, apply when the road is on the same level as the adjacent fields; but in many cases, on the most frequented roads of England, more stuff has been removed from time to time than was put on; the surface of the road is consequently sunk into a trough or channel from three to six feet below the surface of the fields on each side; here all attempts at drainage, or even common repairs, seem to be quite out of the question; and by much the most judicious and economical mode will be to remove the whole road into the field which is on the sunny side of it. In cases where a road is made upon ground where there are many springs, it is absolutely necessary to make a number of under and cross drains to collect the water and conduct it into the aforesaid side-drains, which I have recommended to be made on the field side of the fences.

In constructing the bottom part of a road, (which would, of course, be made of an elliptical form) if it is upon clay, or other elastic substance, which would retain water, I would recommend to cover the whole bottom of the road with vegetable soil, in cases where the natural shape of the ground admits; I would not remove the original surface, and where there are inequalities I would fill them up with vegetable soil, so as to cut off all connexion with clay. Where gravel is the material to complete the road with, I have already mentioned, that it ought to be completely cleansed of every particle of clay or earthy substance, and its different sizes ought to be selected and arranged by means of riddling or washing; in the use of the riddle, the particles of earth or clay adhere so much to the stones that it frequently requires to be exposed to the sun, air, and frost, for several months, and then riddled over again. In this gravel, the stones are of different sizes and different shapes; all those that are round ought to be broken with a small hammer, and in mentioning hammers, I beg leave to draw the attention of the Committee to their weight, shape and manner of using, which is of much more importance than any one can conceive who has not had much experience in road-making; the difference in managing this operation being not less than ten per cent. and is, besides, of equal importance towards the perfection of the road; the size and weight of the hammer I would apportion to the size and weight of the stones, and the stones should be broken upon the heap, not on the ground; it must be evident that using round stones will be the means of deranging the position of those near them, and of grinding them to pieces.

Are you of opinion that the gravel which is found in the pits in the neighbourhood of London is calculated for making roads capable of bearing the heavy weights which the great traffic round London occasions to be used upon them?—I am of opinion that the materials in the whole valley or plain around London being entirely silicious, or flints, and easily ground, to dust, are very improper. This must be evident to every person who travels near London in any direction.

Are you of opinion that it would be advisable or practicable to procure from any particular part of the country, either by canal, or by river conveyance, better materials, so as to form perfect roads, without the necessity of paving them?—That those materials could be procured both by the canals; and by sea is evident; but I am satisfied that the most economical and preferable mode would be by means of paving.

Do you consider that it would be advisable to pave the whole of the roads, or that the paving of the centre or sides, as has been recommended by some witnesses, would be sufficient?—I apprehend that the paving a proper width in the centre would be quite sufficient, gravel might be proper enough for the sides, upon the same principle that we, in all new roads which are constructed, make use of metalling, or broken stones on the middle part of the road, for about from sixteen to eighteen or twenty feet in breadth, and leave the sides gravelled and kept dry; this, in general, forms a very perfect road.

Is there any principle which you would think proper to recommend in regard to the shape of the stones to be used in paving roads?—I am of opinion that the general shape of the stones at present used for paving, and the modes of distributing them are very imperfect, the lower part of the stones being of a triangular wedge-like shape, which, instead of enabling them to resist the weights which come upon them; easily penetrate into the substratum; the stones are also broken of an unequal size. The remedies for these defects are obvious, they should be as nearly as possible of a cubical form, its lower bed having an equal surface with its upper face; they should be selected as nearly as possible of an equal size, and they should never be of great length on the face.

In quarrying and preparing the stones would there be any additional expense in forming them into the cubical shape now recommended?—There would certainly be an additional expense in the preparation, because there would be more work required in the dressing, and many stones must be rejected which are now used; but I think the additional expense would be very well bestowed.

Are you of opinion that great injury is done to turnpike roads by the heavy weights carried in waggons upon them?—I am.

Are you of opinion that any breadth of wheels for those waggons will justify the present exemption from tolls?—It certainly ought not.

In what manner would you recommend that the tolls should be apportioned to the weights carried by waggons on those roads?—I am of opinion that the most advisable mode would be to apportion the tolls to the weight carried on each wheel, without reference to the breadth, provided it is not allowed to be less than four inches.