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\u27s and EWL\u27s. EWL\u27s were computed originally for a 10-yr. period but this practice was revised in 1954, to encompass 20-yr. 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 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)
