The cost of maintaining macadamised roadways as compared with that of granite setts has been said to be as high as 5 to 1 and that this cost if capitalised for 12 or 13 years will equal the first expense, interest on money, and the necessary repairs for a granite paved roadway.
The following table gives the cost per annum per square yard for the maintenance of macadamised roadways in different places, so far as I have been able to collect them:
| s. | d. | s. | d. | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Bristol | 4 | to | 1 | 0 | |||||
| Charing Cross (London) | 5 | 0 | (now paved) | ||||||
| Exeter | 6 | „ | 2 | 6 | including cleansing | ||||
| Glasgow | 8 | ¹⁄₂ | |||||||
| Leeds | 10 | „ | 1 | 2 | |||||
| Liverpool | 2 | „ | 2 | 6 | |||||
| Manchester | 6 | „ | 1 | 8 | |||||
| Merthyr Tydfil | 4 | ¹⁄₂ | |||||||
| Newcastle | 1 | 3 | including watering | ||||||
| Paris | 9 | ¹⁄₄ | „ | 10 | 9 | ||||
| Parliament Street | (London) | 3 | 6 | repairs only | |||||
| Regent Street | (ditto) | 3 | 7 | (now paved with wood) | |||||
| Stockton | 9 | „ | 1 | 6 | |||||
| Sheffield | 1 | 8 | „ | 2 | 0 | ||||
| Wakefield | 1 | 0 | all paved streets now. | ||||||
In Birmingham the macadamised streets have worn down 6 inches in one year, with a traffic of 2484 vehicles passing in 10 hours.
With reference to the great cost of maintenance in Paris, the following particulars[22] may here be given;
“The surface of the street is picked by gangs of men, metal from 2¹⁄₂ to 9 inches in thickness is then laid on, a coating of sand is then spread upon it, it is watered and rolled at per kilometre ton, that is, at per ton weight of roller per kilometre travelled, at a cost of about 15·33d. per ton mile for the first 250,000 ton miles, and at reduced rates for additional service. The materials used for the roads are flints costing 4s. 6¹⁄₂d. per cubic yard for light traffic roads; for medium traffic, hard millstone at 11s. 4d.; and for the heaviest and greatest traffic, porphyry at 15s. 9d. The average total cost of maintenance of the streets is 1s. 8¹⁄₂d. per square yard per annum for the first-class roads, and 1s. 1¹⁄₂d. for the lighter traffic; the highest cost for maintenance is as high as 10s. 9d. per square yard, the lowest 9¹⁄₄d. per annum.”
It may be well to mention that 73 per cent. of the streets in Paris are paved, 5 per cent. are coated with asphalte, and 22 per cent. are macadamised.
The contour, or best form of cross section that should be given to a roadway, has often exercised the minds of engineers, but for all practical purposes evenness of surface and regularity of section in a macadamised roadway are of more importance than the slight difference between straight lines and curves, which might only tend to confuse the workmen. Formerly it was the practice to employ a complicated gauge in the form of a straight-edge fitted with plummet or level and sliding bars, but a good eye, assisted by a long straight-edge and spirit-level and three boning rods, is generally found to be sufficient, and if the centre of the roadway is kept level with the heel of the footpath, a sightly cross-section is generally the result; or say 6 inches to 9 inches higher in centre of a roadway 30 feet in width between the kerbs, 3 inches to 4 inches where it is from 18 to 20 feet in width.
The following detailed section of a macadamised roadway is one which I am in the habit of specifying for suburban districts, as it is easily set out and constructed, and answers all purposes most admirably.
