Road, a solid pathway for the transportation of passengers and commodities. Roads are of various kinds, the degree of perfection to which they have been carried generally corresponding to the degree of civilization of the country where they are situated. The ancient Egyptians must have had hard paved roads on which to transport the immense blocks of stone used in building the pyramids and other structures. The Hebrews had roads at a very early period; the song of Deborah speaks of abandoned highways (Judges v. 6). The Greeks paid much attention to roads, but the greatest improvements, such as permanent pavements, are said to have been made by the more commercial Carthaginians. The Via Ap-pia, called by Statius the queen of roads (see Appian Way), the Via Aurelia (the Tyrrhenian coast road), and the Via Flaminia (see Flaminian Way) were the first great Roman roads, and the Roman empire soon became intersected with numerous paved roads constructed with great care at enormous expense. In many parts they have lasted till the present day.
During the last Punic war a paved road was constructed from Spain through Gaul to the Alps. Similar roads were afterward made in every part of Spain and Gaul, through II-lyricum, Macedonia, and Thrace, to Constantinople, and along the Danube to its mouths on the Black sea; and the islands of Sardinia, Corsica, Sicily, and Great Britain were crossed by them. Under Antoninus Pius (A. D. 138-61) all the Roman military roads were surveyed, including six great roads in Egypt. In India good roads were made at an early period, connecting Agra with Lahore, and Lahore with Cashmere; but after the death of Aurungzebe they fell into decay, and the only good roads in India, it is said, have since been constructed by the British, who have carried a good and metalled road, called the Grand Trunk, from Calcutta to Peshawer on the borders of Afghanistan. The "metalling" (pavement of stone or concrete) of these roads is mostly composed of a calcareous nodule called kunhur found there, which when moistened and pounded into a crust nine inches or a foot deep forms an excellent pavement. The kunkur is sometimes ferruginous, which improves its quality. In ancient Peru the Incas built great roads, the remains of which still attest their magnificence.
The most remarkable were the two which extended from Quito (or in fact nearly 100 m. N. of Quito) to Cuzco, and on toward Chili, one passing over the grand plateau, the other bordering on the ocean. Humboldt, in his "Aspects of Nature," says of the mountain road: " But what above all things relieves the severe aspect of the deserts of the Cordilleras are the remains, as marvellous as unexpected, of a gigantic road, the work of the Incas. ... In the pass of the Andes between Mausi and Loja we found on the plain of Puttal much difficulty in making a way for the mules over a marshy piece of earth, while for more than a German mile our sight continually rested on the superb remains of a paved road of the Incas, 20 ft. wide, which we marked resting on its deep foundations, and paved with well cut, dark porphyritic stone. This road was wonderful, and does not fall behind the most imposing Roman ways which I have seen in France, Spain, and Italy. By barometrical observation I found that this colossal work was at an elevation of 12,440 ft." Prescott says : "Galleries were cut for leagues through living rock; rivers were crossed by means of bridges that swung suspended in the air; precipices were scaled by stairways hewn out of the native bed; ravines of hideous depth were filled up with solid masonry - in short, all the difficulties that beset a wild and mountainous region, and which might appal the most courageous engineer of modern times, were encountered and successfully overcome.
The length of the road, of which scattered fragments only remain, is variously estimated at from 1,500 to 2,000 m. Its breadth scarcely exceeded 20 ft. It was built of heavy flags of freestone, and in some parts at least covered with a bituminous cement, which time has made harder than the stone itself. In some places, where the ravines had been filled up with masonry, the mountain torrents, wearing on it for ages, have gradually eaten a way through the base, and left the superincumbent mass - such is the cohesion of the materials - still spanning the valley like an arch." - The Britons failed to keep up the roads made by the Romans, or to construct new ones, and for centuries they used bridle paths, or at most narrow passages for small carts; and not till the 16th year of the reign of Charles II. was there any attempt by the government to improve the roads. The first turnpike road was then established by law; but it was not till about a century ago that a system of good roads was established. Up to that time goods were conveyed in Scotland on pack horses. In 1770 the journey from Liverpool to Manchester, according to the account of Arthur Young, was not a little perilous from the bad condition of the road.
But within the next 60 years, when the manufacturing resources of the country, through the introduction of the steam engine and the extensive use of coal, were developed, the progress in road making was rapid. In the United States the importance of roads for military purposes, leading into the interior territories and to the frontier, was early appreciated, and some important routes were opened by the general government; as the national road from Baltimore, through Wheeling and Cincinnati, to St. Louis, and that from Bangor to Houlton in Maine. The making" of turnpike roads by chartered companies, before the general introduction of railroads, often yielded much profit to capitalists. Most of the paved road was constructed upon the Macadam principle. Several public turnpikes have been constructed in parts of New York and in the western states with planks; but they have not proved successful, as the exposure to air and moisture causes them to decay rapidly. - In laying out a new road, the general system resembles that for the construction of railways, but an equal expense in securing level grades is not usually justifiable.
It is found that upon a slope of 1 in 44, or about 120 ft. to the mile, a horse can draw only three fourths as much as he can upon a level; on a slope of 1 in 24, or 220 ft. to the mile, only half as much; and on a slope of 1 in 10, or 528 ft. to the mile, only one fourth as much; but these proportions vary with the condition of the road, because when the road is soft the grade is virtually increased. The harder and firmer and smoother the surface of a road is, the less resistance it will offer to a passing wheel; and for this reason elastic road beds are inferior for the transportation of heavy loads. It is usually estimated that the greatest inclination down which horses may trot with safety is, for roads paved with blocks, 1 in 60; for macadamized roads, 1 in 35 or 40; and for gravel or dirt roads, 1 in 15. In regard to the surface of a transverse section of a road, there has been considerable debate, some maintaining that it should be nearly straight, and that the drainage should be secured when practicable by longitudinal grading, the reason being that ease of draught on a convex road requires the wagon to be in the middle of the track. The weight of authority seems to be in favor of raising the track in the middle, but not to such a degree as to cause much inclination of the wagon.
On roads where there is much traffic, so that wagons are continually meeting and passing, inclination may be avoided by having two tracks, each raised in the middle. To allow the water to run longitudinally upon a road bed for any considerable distance will certainly cause any macadamized or stone pavement to get out of order, from washing or undermining, unless it is laid in hydraulic cement, or asphalt of sufficient firmness to resist the action of a rapid current of water. In regard to the formation of the road bed there are two systems, that of Telford and that of Macadam. The system of Telford is principally a revival of that employed by the old Romans, and also adopted by Trésaguet in France in 1760, but discarded in 1816 by Macadam, who substituted small angular broken stones, laying them directly upon the earth. (See Pavement.) Telford made a return to the system of laying heavy stones at the bottom of the bed and covering them with a coating of broken stones. Several excellent roads were constructed by him in Great Britain, the permanence of which is evidence of his engineering wisdom, such as that between Holyhead and Shrewsbury, and the Glasgow and Carlisle road. Macadam preferred a yielding to a rigid foundation, and even laid broken stone upon boggy ground.
The angular shape of the stones caused them to bind together somewhat, but the superiority of roads having large stones or concrete (which is preferable since the manufacture of hydraulic cements has become so general) for a foundation is now generally conceded. The kind of stone most suitable for a road bed is a matter of importance; for macadamized roads, granite or basaltic rock, covered with sandstone or argillaceous shale, is to be preferred. Slate rock in various degrees of hardness may often be employed with advantage as a surface covering as well as a filling in many kinds of pavement where hydraulic cement is not relied on to produce firmness. Of the drainage of a road not much need be said, as it is evident that it should be comparatively dry, and not subject to inundation. A ditch at one or both sides, when the land does not slope away, is almost always necessary, and culverts to lead the water from one side to the other. In carrying a road over a hilly country it is usual to wind around the sides of hills and mountains, and an inclined plane of considerable length often becomes necessary.
A ditch upon one side, with frequent culverts, should be constructed; but it is sometimes the practice on turnpikes built by companies, and where the income of the road would not justify the outlay for construction and repair of culverts, to make diagonal elevations across the track at frequent intervals to direct the water off the road. If they are placed too far apart, the water is suffered to gather too much headway and thus wear away the road bed. It is this accelerated movement of water in the ditches of a road running down hill that makes it so difficult to construct culverts which shall receive the current and conduct it away without damage to the banks along the roads. - Public roads are laid out, constructed, regulated, and kept in repair by public authority. Private property is taken for the construction of roads upon allowance of just compensation to the owner. The system of making assessments for repairs varies in the different states. Generally all property owners in the town or county where the road lies are assessed. In many of the states all male inhabitants 21 years old or over are required to labor on the roads a specified number of days each year, but a substitute may be furnished or commutation be made in money.
Females are subject to a property but not to a labor assessment. In large cities spe6ial regulations generally prevail. - Among the most important works relating to roads are Macadam's " System of Road-making" (London, 1825); Parnell's "Treatise on Roads" (1838); Telford's reports to parliament on the Holyhead road; Penfold "On Making and Repairing Roads" (1835); Ponce-let, Mécanique industrielle (Paris, 1841); Mo-rin, Aide-mémoire de mécanique (1843); Gayf-fier, Manuel des ponts et chaussées (1844); and Gillespie, "Roads and Railroads: a Manual for Roadmaking" (10th ed., New York, 1871).