The Highway Capacity Manual (HCM) is a publication of the Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine in the United States. It contains concepts, guidelines, and computational procedures for computing the capacity and quality of service of various highway facilities, including freeways, highways, arterial roads, roundabouts, signalized and unsignalized intersections, interchanges, rural highways, and the effects of mass transit, pedestrians, and bicycles on the performance of these systems.