A NEW LOOK AT HIGHWAY CAPACITY

For many decades, transportation planners have been concerned with the study of highway capacity in order to keep the operation of existing roads and the design and construction of new roads functional with the consideration of the high number of vehicles that use them. The problems associated with costly major highways, especially in urban areas, greatly increases the need for better street and highway capacity information in order to increase efficient use of old and new facilities. The Highway Capacity Manual, published in 1965, emphasizes capacity aspects of freeways and special problems that need to be included such as weaving sections and ramp terminals. The manual also reviews other highway types such as urban arterials, downtown streets, rural multilane and two-lane roads, at-grade intersections, and bus transit operations. This article reviews the Highway Capacity Manual in detail by chapter and covers definitions, traffic characteristics, capacity and level of service, capacity and service volumes, at-grade intersections, weaving, ramps, freeways and other expressways, streets and highways without access control, and bus transit.