Researches on the Structural Design of Highways by the United States Bureau of Public Roads

The United States Bureau of Public Roads, in connection with its extensive work on Federal Aid Roads, has been authorized to do considerable research involving various phases of highway design and construction. This work has been carried on in different localities and with several co-operative agencies, but largely from the main office and at the Experimental Farm in Arlington, Va. This paper treats only those phases of the research concerned with the structural features of highway design, considered under (1) researches on the sub-grade; (2) loads on pavements; (3) stresses in concrete pavements; (4) Pittsburg, Calif., test road; (5) studies in materials; and (6) miscellaneous investigations. In all cases, the scope and procedure of the test project is given, results are described, and conclusions drawn. Although certain phases have yielded conclusive results, the work on highway research, as a whole, is far from complete; this paper simply aims to acquaint engineers with some of the accomplishments to date and to stimulate further development.