Freeway Planning Methodology

Abstract

A major new chapter of the Highway Capacity Manual (HCM) 2000 is on freeway facilities. It is a detailed operational methodology that combines analyses of basic freeway segments, weaving areas, off-ramp areas, and on-ramp areas. However, the new chapter does not contain guidance or examples for planning or preliminary engineering applications. To meet its numerous needs, Florida Department of Transportation engineers wanted to develop a freeway facility application that extends the HCM for generalized planning and preliminary engineering purposes but is not inconsistent with HCM 2000. Such a methodology was developed, documented, made into an executable software program called FREEPLAN, and is now being implemented throughout the state. The methodology is firmly based on HCM detailed analysis procedures but has assumptions and defaults that allow planners and engineers to use it effectively. At a generalized planning level, the basic construct was to provide tables of design volumes, v, and annual average daily traffic that could be achieved for various levels of service and freeway configurations for the default parameter values. At a preliminary engineering level, specific freeway facility inputs are used to determine v/c ratio, average travel speed, average density, and level-of-service grades. The initial results of applying the Florida freeway planning methodology to actual Florida data were outstanding in both urbanized and rural areas.