In design of freeways the various geometric features, the configuration and spacing of interchanges, the number and arrangement of lanes, must be determined largely through level-of-service and capacity analyses. The 1965 Highway Capacity Manual basically furnishes this discipline, but it is not sufficiently oriented to design application, and lacks certain data and procedures. To meet these requirements the discussion herein develops a procedural framework for analysis. As part of the developed procedure, gaps in the Manual presentation dealing with ramps with high peaking characteristics are filled in by re-evaluation and more detailed rationalization of data and methods in the Manual, and by application of some data from other sources. A special feature of the technique involves the grouping of successive ramps along a freeway into overlapping pairs. The influence of one ramp upon another is then isolated and each component of the freeway is dealt with by a separate analysis. Finally the results are combined to reach a composite solution for design of the complete freeway facility or for it as an operating system. A graphical method, utilizing special nomographs, has been deveolped to facilitate the procedure. A series of illustrative problems and their solutions are presented, covering the full scope of problems to be encountered. Accordingly, the publication considers fully the aspects of practical application, and is presented to serve as a complete guide for level-of-service and capacity analyses in design and redesign of freeway facilities. (Author/publisher)
Abstract