The Kentucky Department of Highways, in 1946, sought a more systematic criteria and basis for designing the thickness of bituminous concrete pavements. The Research Division was authorized to pursue this work and to develop the criterion. These efforts were embodied in a report (1) to the Department, which offered a system of design based upon CBR's and EWL's. EWL's were computed originally for a 10-year period but this practice was revised in 1954 to encompass 20-year traffic (more realistic with respect to average road life). Then, in 1957, the Department requested a re-evaluation of the criteria from the standpoint of experience and performance of pavements designed thereby. This re-study, and recommendations therein, was reported to the Department and to the Highway Research Board (2)(3). A copy of current design chart is shown on the following page (Fig. 20, Ref. 2 and 3).

Report Date


Report Number

No. 172a

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