The Highway Capacity Manual (HCM) is commonly used by transportation agencies to evaluate the current or forecast operations of roadway facilities. Less well known is that the HCM can also be used to cost-effectively and reliably support agencies’ planning, programming, and management decisions. This Planning and Preliminary Engineering Applications Guide to the HCM (“Guide”) is intended as a reference and educational resource on best practices for applying HCM methods to a variety of planning and preliminary engineering applications. It is designed to improve planning practice by identifying appropriate techniques for utilizing the HCM in planning and preliminary engineering analyses and to illustrate these techniques through the use of case studies. It is intended to be used by planners, engineers, and system analysts at various stages of the system management, operation, planning, and project development process.