Introduction
Illinois was the first state to have its entire section of route 66 completely hard-surfaced. In 1918, Illinois voters approved a $60 million bond issuance to finance the construction of approximately 4,800 miles of hard road state highways.
At the 1919 annual meeting of AASHO, Anson E. Marston, dean and director of the engineering department at Iowa State College, and later President of ASCE in 1929, presented a plan to the State highway officials: “The country is about to spend untold billions of dollars in the construction of paved roads. Yet there is a very serious lack of the fundamental scientific data which are absolutely essential to the correct design and construction of paved roads.”
AASHO responded by influencing construction of the Bates Experimental Road near Springfield to investigate important factors involved in the rational design of pavement surfaces. Clifford Older, Chief Engineer of the Illinois Highway Department, published the results of this study in the 1924 Transactions of ASCE as Paper No. 1546, entitled, "Highway Research in Illinois", and in Bulletin No. 18 of the State of Illinois.
Building on the success of the 2018 bond issue, an additional $100 million in bonds was approved in 1924. By the end of 1926, all of the $60 million State Bond Issue for road construction had been contracted, and SR4, renamed to Route 66, was paved from Chicago to East St. Louis.
Over the next several decades, the legacy of the Bates road test eventually extended well beyond the borders of Illinois. As one of the best-documented initiatives of its kind during that era, the Bates Road Test helped set the stage for larger-scale efforts that were also undertaken to assess the most optimal materials and designs for the development of long-lasting roads. These efforts included several loading tests on concrete pavement that were conducted by the U.S. Bureau of Public Roads in the 1930's. A later road test in 1958 to 1960 by AASHO in Ottawa, Illinois, established design parameters for roads and bridges on the Interstate system.
From the early 1960s through 1993, all versions of the AASHTO Guide for Design of Pavement Structures were based on limited empirical performance equations developed at the 1958-1960 AASHO Road Test. The need for and benefits of a mechanistically based pavement design procedure were recognized when the 1986 AASHTO Guide for Design of Pavement Structures was adopted. To meet that need, the AASHTO Joint Task Force on Pavements, in cooperation with the National Cooperative Highway Research Program and the Federal Highway Administration, sponsored the development of the Mechanistic Empirical Design Guide under NCHRP Project 1-37A.
References
International Society for Concrete Pavements - Bates Road Test
Sangamon County Historical Society - Bates Experimental Road
Illinois Division of Highways on the Bates Experimental Road project
Modern highways got start in Sangamon County
International Society for Concrete Pavements - AASHO Road Test - Ottawa, IL, 1958-1960 AASHO Road Test
Historical Concrete Pavement Explorer - AASHO Road Test - Ottawa, IL
Flexible Pavement Design - State of the Practice, National Center for Asphalt Technology
National Park Service - Illinois Road Segments