COM 0574.005 1996-1998 - Laserfiche WebLink

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• + ABSTRACT OF METHODOLOGY for the LEVEL OF SERVICE ANALYSIS OF UNSIGNALIZED INTERSECTIONS This abstract summarizes the procedures for analyzing the capacities of unsignalized intersections. These procedures are described in the Highway Capacity Manual, Special Report 209 (Third Edition, 1994) by the Transportation Research Board (TRB). This manual "is a collection of techniques for estimating highway capacity that have been judged, through consensus, as the best available at the time of publication." This manual does not set legal standards for highway design but the procedures have become widely accepted and used in the traffic engineering profession. The capacity analysis procedure is based on a German method originally published in 1972 and translated in 1974, and modified for U. S. conditions by the TRB in 1985, and new data reflected in 1994. It is intended for two-way STOP- and YIELD-controlled intersection and calculates the capacities of movements which cross or turn through the major traffic stream. The capacity of each movement is based on two factors: the gap distribution in conflicting traffic streams and the gap acceptance behavior of drivers at such intersections. The basic steps in methodology are as follows: 1) Define intersection geometry and traffic volumes. 2) Determine the "conflicting conflicts" through which every minor street movement and major street left turn must cross. 3) Determine the size of the gap in the conflicting stream needed by vehicles in each movement crossing a conflicting traffic stream. 4) Determine the capacity of the gaps in the major traffic stream to accommodate each of the subject movements that will utilize these gaps.