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Show ROAD'-" MlfLilMS SCRUBBING-BOARD SURFACES D'jreau of Public Roads Building Experimental Ex-perimental Highway to Determine Deter-mine Cause of Waves. (I'rapured hy thfi Unlli-'t Htalia Department uf Agriculture ) What mum a "turred" road to develop de-velop that peculiar scrubblng-board surface Is a question that has been worrying tho highway engineers quite as much as the long-suffering public As often as not the symptoms appear In a macadam road that has been treated with asphalt. Hut the trouble Ih largely confined to roads built with tar or asphalt. Concrete and brick roads never develop such a surface, and ordinary dirt roads seldom do. The bureau of public roads of the United States Department of Agriculture Agri-culture Is bullcftng at the Arlington (Va.) experimental farm nil cxperi-menlal cxperi-menlal roadway 15 feet wide In an attempt at-tempt to discover the cause of the trouble. Tbo road Is laid out In the form of a circle with a 00-foot radius and Its circumference, K05 feet In length, Is to be divided Into sections, each of which will be surfaced with a different kind of asphalt or tarred Btirface. Tho experimental sections will be built exactly like actual road surfaces uiid when completed they will carry a "traflic" as much like actual traffic as It Is possible to devise. The "traffic" "traf-fic" will be supplied by a driverless motortruck which will be held to the circular path by means of a long arm extending from the center. The course of the truck will he altered from time to time so that the entire width of the roadway will be traveled. It bus not been possible to determine the cause hy observation of actual roads because there are too many unknown un-known quantities. The defect may be due to distortion of the earth under the road surface or to defects In the surface itself. It Is probably caused I - Treating the Surface of a Macadam Road With Bituminous Material. In some way by the wheels of motor vehicles how and why the engineers have not determined, largely because they have never possessed all the facts with regard to surface and subsurface conditions and character and weight of traffic. |