Page:America's Highways 1776–1976.djvu/451

 a wooden wagon. But changes were starting to take place. The Office of Road Inquiry, established in 1893, sent engineers to various parts of the country to construct object lesson roads in order to demonstrate that year-round good roads were possible and to show the proper roadbuilding methods to achieve them. In machinery, the steam shovel and steam roller were already in limited use but the new steam tractor, with its broad iron wheels, foreshadowed the retirement of the horse and mule from the road construction scene.

Grading a new location at a washout in 1914. At right a man uses a plow to form a ditch, others drive horsedrawn wheel scrapers. Steam shovels were used for excavation work in the early 1900’s, but dump wagons were still horsedrawn. Bottom dump wagons, shown here, were especially useful for dumping heavy, sticky material.

After the turn of the century, there were some very significant happenings which had quite an influence on the future of road construction. The Office of Public Roads (OPR) engineers continued to teach others how to build and maintain good roads under the object lesson roads program while also studying and investigating new methods themselves. The small Federal laboratory in the OPR developed tests for aggregates and other materials and made important contributions toward overcoming defects in early bituminous construction. Public Roads engineers determined and published typical specifications for highway construction, the first of which was in 1913 concerning the fabrication and erection of steel highway bridges.

With the coming of the automobile, the macadam and earth roads caused quite a dust nuisance in dry weather. However, it was also about this time that people realized that oil could be used as a road material. It was found that a road covered with oil would be free from dust in the dry season, yet hard and firm in the wet season. This led the way to early experiments with tar and bituminous material to improve road surfaces. 445