This book is formulated to establish uniformity for technical standards of highway substructure design and to make substructure engineering design meet the requirements of safety, reliability, technical advancements, economy, and rationality. It is applicable to the substructure design of the new construction and expansion of all classified highways. The 'substructure' in this book includes the whole parts of highway trapezoidal cross section. That is to say, it is generally referred to as general facilities, not only the subgrade, but also the slope protection, drainage, and retaining wall are included.