الفهرس 
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Abstract
Recent studies and observations conducted on the behavior of highway
pavements, have emphasized the variabilities in the magnitude and distribution of traffic loading, in the properties of pavement materials, and in the enviromnental conditions. These variabilities will inevitably result in some degree of randomness and uncertainties in the response of pavement structures to these factors, which should also be accounted for in the evaluation of performance of the pavement structures.
The rapid increase In the number of Equivalent Single Axle Loads
(ESAL) passing over the pavement surface and the high construction and
maintenance costs emphasis the need for a rational method of analysis and
design based on a tme representation and understanding of the contribution
which each element of the pavement structures and the surrounding
environment makes to the overall deviation of pavement performance.
Traditionally, the uncertainty of prediction of the future behavior of
constructed facilities is accounted for by including safety factors in designs.
The effectiveness of these safety factors varies with the degree of variation of the parameters they modify. The use of higher safety factors when one is less certain (or- when the consequences of loss are greater) is an implicit recognition
of this fact. In ’many cases, however, there can be substantial overdesign and
misallocation of resources because safety factors are too large for the actual uncertainties involved.