The Highway Capacity Manual (HCM) was first published in 1950 to address highway planning, design, and operations. Throughout its 75-year history, the HCM has evolved to meet transportation planning and engineering needs, especially as agencies attempt to incorporate modes beyond motor vehicles. This evolution has resulted in additional methods, increased complexity with analyses, and results that can be difficult to convey. The scope and scale of the current (7th) edition of the HCM seems to be lessening rather than increasing many users’ understanding of the contents, including methods and calculations, and there is growing concern that practitioners are increasingly relying on proprietary software to help with analyses. Often, practitioners must use more than one proprietary tool in tandem, or seek methods developed outside the scope of the HCM to conduct their analyses.
