UNIFORM CRITERIA FOR LEVEL-OF SERVICE ANALYSIS OF FREEWAYS

For level-of-service analysis, the 1994 Highway Capacity Manual divide s freeways into basic sections, ramps and ramp junctions, and weaving areas. Different criteria are applied to these components to define le vels of service. This use of nonuniform criteria makes it difficult to assess operating consistency in terms of the spatial change of traffi c operations throughout a freeway system. This problem can be alleviat ed by using vehicle speed to establish a set of uniform criteria for t he systemwide evaluation of freeway design and operation. Toward this end, the relationships between speed and other related geometric desig n and traffic parameters should be established. The spatial variations of flow characteristics on freeways, and the need to account for such variations in capacity and level-of-service analysis, are discussed f irst by analyzing observed speed-how relationships. This is followed b y a discussion on the selection and application of uniform criteria fo r planning and design.