This book presents peer-reviewed articles from the 18th Conference of the Associated Research Centers for the Urban Underground Space (ACUUS 2023) held in Singapore from November 1 to 4, 2023. It highlights new opportunities and challenges in underground space use amid a re-focus on exploring and developing the underground space as a strategic resource and part of sustainable development. The new frontier presents unprecedented opportunities for simultaneously improving urban infrastructure, urban livability, and resilience. At the same time, special challenges exist in developing underground space—both from a human design perspective and in terms of complexity, 3D planning, system integration, technical, and life cycle costs. Equally important is the need to move from the creation of underground space as a haphazard, last resort solution to a well-planned, and integrated use of underground space that can serve the needs of society for future generations as well as our own. As the world emerges from the COVID-19 pandemic and is faced with the many challenges in climate resilience, the works presented in this book provide a timely opportunity and an excellent forum for engaging discussions and exchanges among planners, designers, engineers, researchers, and policy makers.

The book considers the underground development of cities from a systemic point of view. The authors' scientific methodology for planning a system of alternative design configurations in a metropolis (including underground infrastructure) on the basis of applied system analysis methods is revealed. The book presents a short guide and a number of practical applications of morphological analysis, cognitive modeling, and other system analysis methods as tools for solving various urban problems, including risk assessment in the transport infrastructure of a city; evaluation and justification of constructing different types of underground objects on a selected site according to its structural, functional and geological factors; construction of scenarios aimed at informed decision-making in planning complex underground facilities. The book provides novel and convenient tools for urban development to professionals in urban planning, municipal authorities and investors, and researchers in urban studies.

Backpacker brings the outdoors straight to the reader's doorstep, inspiring and enabling them to go more places and enjoy nature more often. The authority on active adventure, Backpacker is the world's first GPS-enabled magazine, and the only magazine whose editors personally test the hiking trails, camping gear, and survival tips they publish. Backpacker's Editors' Choice Awards, an industry honor recognizing design, feature and product innovation, has become the gold standard against which all other outdoor-industry awards are measured.

February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index.