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SUMMARY In January 1993, Be University of Idaho, in cooperation with Kittelson and Associates, Ruhr University, and Queensland University of Technology, initiated work on NCHRP 346 to develop new capacity and level of service analysis procedures for unsignalized intersections. This report is Me second of two volumes documenting He work completed for this project. Volume one describes the work completed for two-way stop-con~olled intersections. Volume two includes eight chapters documenting He work completed for as-way stop- con~olled (AWSC) intersections. A new data base describing traffic operations at AWSC ~ntersecdons was assembled as part of this study. Thirty unique sites were videotaped during 41 different time penods. In most cases, four video cameras were used at each site producing over 150 individual videotapes. A total of 151.67 hours of usable data was acquired. Field observations chow Hat AWSC intersections operate in either two-phase or four-phase patterns, based primarily on He complexion of the intersection geometry. Flows are determined by a consensus of right of way that alternates between the north-south and east-west steams (for a s~ngle-lane approach) or proceeds in turn to each intersection approach (for a multi-lane approach intersection). The basic parameter used to compute intersection capacity is saturation headway. Based on data from over 22,000 vehicle records, it was found dlat He saturation headway is dependent on (~) He degree of conflict faced by the subject driver as measured by He presence of vehicles on the opposing and conflicting approaches, (2) the ~ntersechon geometry, particularly He number of lanes on He conflicting approaches, He opposing approach, and He subject approach, (3) the directional movements of the interacting vehicles, and (4) the vehicle type. New models for estimating saturation headway, service ~me, capacity, and delay are recommended. The models were subject to a series of validation tests using the data collected as part of this study. Level of service forecasts produced by He new set of models are of better quality than those produced by He existing 1994 HCM Update procedure. ~ addidon, the severe range restrictions now a part of He 1994 procedures will no longer apply Bus giving He practicing traffic engineer He capability to produce good quality forecasts for a much wider range of traffic conditions Man is possible today. . . ,
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