Familiarity with geotechnical aspects of pavement engineering is essential for the practicing pavement engineer. When designing pavements, accurate characterization of the existing subgrade condition becomes a crucial task. In the past, traditional geotechnical exploration and testing methods have been used to characterize existing subgrade conditions. However, with the introduction of the Mechanistic-Empirical (ME) pavement design, there is a need for improved and more appropriate methods of subgrade characterization, for prediction of future pavement conditions with better accuracy. Hence, this handbook will present a useful tool for practicing pavement engineers.