الفهرس 
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Abstract
In the last decades, the importance of highway is increased because it is
considered a measure of civilization of any country and due to the increasing of
motorisation. The policy of improving highway system depends on two techniques.
The first, for existing highways, is the proposing of the most rapid and economic strategy of maintenance. The second, for new highways, is the selection of design method which suits the Egyptian conditions to reduce the cost of maintenance.
This study is concerned with the proposing of the suitable design method for the Egyptian conditions. Data concerned with traffic analysis, subgrade, aggregate,
climate, and pavement conditions in Egypt were collected. A comparative study of recent flexible pavement design method ”AASHTO, Asphalt Institute and California Stabilometer” has been carried out through their input parameters and characteristics of each design method. Thickness omparison and sensitivity analysis, for some cases of study, which cover a wide area of Egyptian conditions,
were investigated to evaluate the relative importance of input parameters, and to provide insights into the relative change in required thickness (SN) of the pavement structure that would result from changes in the input parameters. The
analysis revealed that variation in sub grade strength has the most pronounced
effect on structure number than variation in traffic load, for the selected design methods. Also, the California Stabilometer design method can be considered the most reliable method to be adopted in Egypt, with some modifications. An application of the proposed design method was carried out on some samples of subgrade from different regions of Egypt after fabrication of exudation and
expansion pressure apparatuses.