Tests in the early 1920s and later studies showed that the service life of a highway pavement is related to the magnitude and frequency of the wheel loads, to the characteristics of the pavement and its substrate, and to the environment. Efforts to quantify these relationships led the American Association of State Highway Officials (AASHO) to conduct the historic Road Test in the late 1950s. Contributions from the 48 contiguous states, Hawaii, the District of Columbia, and the territory of Puerto Rico financed this major undertaking. The U.S. Department of Defense provided a unit of 300 to 400 soldiers to drive the test vehicles. The total cost of the project was approximately $27 million, including $12 million for research, $12 million for construction, and $3 million in contributed services.
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