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ROAD CONSTRUCTION
Page 70
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In America
America Has its Big Problem of Dirt Roads Awaiting Conversion. Why 19 Times Britain's Mileage Costs Only Six Times as Much
Annually By Our Special Representative
THE big total road mileage of America is somewhat discounted by the fact that, at the moment, for each mile of the combined totals of all types of hardsurfaced road (State and County) there are 3.6 miles of " earth " or " dirt " roads.
The distinction between "earth" and " dirt " is a little difficult to follow, but there is nothing subtle about it. American highway engineers know the " earth " road as a "dirt" road which is topped with selected earth. It seems strange to the English mind that over 21 million miles of American public roads should have their surfaces made by the simple process of carting earth from the adjacent land, spreading it roughly and leaving it to be consolidated by the traffic. Yet that is the situation. The big problem ahead is the improvement of a large proportion by the imposition of hard surfaces.
"Dirt" and "Earth" Roads.
America's conversion of a big mileage of "dirt" into " earth " roads represents the first. stage in evolution. The earth is selected. The step-up may, perhaps, in a sense other than as to standard, be compared with our intermediate classificationof • British scheduled roads. In the. U.S.A. it is step No. 1 from -the worst type of public road. Let there be no mistake. The British unclassified road at least has a hard surface and some foundation. The American 21 million miles of " dirt " and " earth " -roads are a slough ef despond in wet weather and a dust hades hi ,dry weather. • •
• But they are being tackled with a in the lowest scale by the incorporation: of chosen earth instead of -the nearest top-soil, in the next scale by mixing in sand and clay, in the next by treated or untreated gravel, chert or macadam, in the next by
spraying tar and bitumen (penetration), in the next by laying and roll
ing prepared metal of higher charac teristics, next an asphaltic carpet, and thereafter, by high-class recon struction throughout—good foundations, plus concrete at choice. Every credit must be given to the American c4 Bureau of Public Roads for its energy and success.
America has 48 States, and these are divided into counties. Virginia, for example, is divided into 100 counties, North Carolina into 100, South Carolina into 146, Georgia into 161 and Florida into 66. Many of those who attended the recent International Road Congress at Washington have been marching (by motor coach) not only through Georgia but along some 2,000 miles of all kinds of highway in the five States mentioned. It will be observed that the counties are not so large in area as are those at home, owing to their greater numbers.
A Summary of Road Data.
It will convey to British readers some idea of the Magnitude of America and the greatness of her road outlook if some data obtained during that tour are summarized. Here they are :— Virginia.—An area of 40,262 sq. miles, a public-road mileage of 59,080, of which 7,132 are in the State highway system, and of these 3,534 entitled to Federal aid. It is opposed to borrowing for new highways or for acceleration of improvements. Virginia pays as it goes, chiefly by means of a petrol tax of 5 cents a gallon. It uses convict labour extensively and has laid 771 miles of Portland cement concrete.
North Carolina.—An area of 48,686 sq. miles, a public-road mileage of 68,798, of which 8,798 are in the State highway system, and of these4,230 entitled to Federal aid: It believes in borrowing, and has bond issues for highways amounting to $115,000,000. It also has a 5-cent petrol tax, and has laid 1,348 miles of asphaltic concrete and 2,295 miles of Portland cement concrete. It is the most progressive of States.
South Carolina.—An area of 30,989 sq. miles, a public-road mile age of 52,318, of which the State highway system comprises 5,9813,178 entitled to Federal aid. South Carolina relies chiefly on a petrol
tax of 6 cents per gallon, this being the highest rate in any State—
Florida and Georgia alone equal this of all the 48 States. It has laid only 1,346 miles of hard-surfaced roads, 906 miles being Portland cement concrete.
Georgia.—An area of 58,980 sq. miles, a public-road mileage of 78,521, of which 7,124 are in the State system and of them 5,497 rank for Federal aid. This State has no bonded debt. A total of 2,023 miles are hard-surfaced, 812 miles being Portland cement concrete.
Florida.—An area of 59,400 se. miles, a public-road mileage of 50,000, of which 8,937 are in the State system. The length entitled to Federal aid is 1,926 miles. Much of this State is marshy and a high proportion of it is rural roads, but approximately 10,000 miles of all its public roads have been hard-surfaced. Portland cement concrete is favoured on the main roads.
exact figures are obtainable.
Federal aid amounts to 50 per cent, of the cost of construction, with a limit from Federal sources of $15,000 per mile. It was initially limited also to 7 per cent. of the mileage of public roads, but this is reviewed and increased from time to time. The other 50 per cent, of construction cost (or more if the road costs above $30,000 a mile to build) falls on the State. Bridges rank similarly for 50 per cent. Federal aid. There is no grant towards maintenance: this falls wholly on the respective States and their county divisions.
America's Size.
If any two of the foregoing State areas be added together, the area of Great Britain is equalled or ex-. ceeded. The total area of America is little short of 40 times that of Great Britain, her mileage of ;public roads is roughly 19 times as great and her annual aggregate expenditure on them is only about six times as great. It is the last of these multiples that tends to show the low average standard of American highways taken 'as a whole.
It is too early to segregate the annual total cost for America's 662,000 miles of hard-surfaced roads and to compare it with that of Great Britain's total of 160,000 miles. No " dirt" or " earth " roads enter into the British records. All are metalled or paved; Amongst all features of America's highway engineering is that of super-elevation at curves. This varies, on her modern highways, from 6 per cent. to 14 per cent. It sounds (and looks) Very considerable. Curves of 80 ft. or 90 ft. in radius can with comfort be taken at 25 m.p.h.' by laden coaches. Without the heavy banking noted 8 m.p.h. might be the limit.