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Show GENERAL TYPES OF I HIGHWAYS IN USE j One of the most remarkable features fea-tures of the gigantic road building program this country is engaged in Is the diversity of road types adopted to meet varying conditions of traffic, location lo-cation and available funds. The adoption adop-tion of, various types of roads marks the severance from Old world construction con-struction which has always held to one type of road ; and ushers in a new era of road building where the road is adapted to the conditions It will be called upon to meet. Generally speaking the present-day plan advocates the construction of the highest type of road possible, keeping the road, however, within the boundaries boun-daries of Its possible earning power. Roughly, there are four types of roads now in use. These are the graded but unsurfaced roads, the lighter light-er type surface with natural binder, the lighter type surface with artificial binder and the base type. The mileage of roads in the country, coun-try, some 3,000,000 miles, is so great and the traffic over many miles so light that building hard-surfaced roads over more than a relatively small percentage per-centage of the total mileage will .be impossible for years to come. This does not mean that our road builders are neglecting these lightly traveled stretches. These roads are being Improved Im-proved through grading and draining so that as little trouble as possible with mud, dust, and impassability will be experienced. In the South and some other parts of the country saud-clay saud-clay roads are coming into favor, the sand, packed with the natural surfacing, surfac-ing, forming a fairly good surface. While this lower type of road serves its purpose with some facility, traffic of any density necessitates large maintenance main-tenance expenditures. The next higher high-er type of road, the surfaced with natural nat-ural binder, then becomes necessary. In this classification are gravel, water-bound water-bound macadam, and crushed rock. These surfaeings may be put on and compacted under heavy rolls, or they may be laid with a water binder. Because Be-cause there is little resistance to raveling rav-eling and tearing action, traffic soon wears this type out. The type of road composed of rock, i gravel or macadam bound together ! with asphalt or some other type of ar-! ar-! tificial binder has found much favor I on roads with only a moderately heavy I traffic. In this type of road the sur-; sur-; facing material Is laid and compacted : and the binder material spread over the surface. Penetration of the binder ! ties the particles of surfacing together, forming a sheet which resists the wear and tear of traffic with reasonable ease. Under careful vigilance this type of road has been found well suited to the secondary roads of the nation, but under un-der main line traffic the maintenance is too excessive to make this type of road popular. This is especially true of roads where there is a great deal of bus and truck traffic, for the pounding pound-ing of these heavy vehicles requires a hard-road surface which cannot be torn apart. |