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115 <br /> Appendix 131 : Urban Streets — Arterials and Collectors/Locals <br /> (also used for On-Ramps and Off Ramps, not normally associated in systems planning) <br /> The equation below is an approximation of the "ultimate capacity" (LOS E) of an urban street <br /> (arterial). However, HCM does not provide a single equation which estimates the capacity of urban <br /> streets at other Levels of Service (e.g. at LOS D). Instead, the detailed procedures and equations <br /> described in HCM Chapters 15 and 16 must be used in order to manually calculate urban street <br /> capacity. The equation for estimating "ultimate capacity" (LOS E) of urban streets is provided <br /> below because it shows the factors which influence capacity of these facilities. Following the <br /> equation and table of adjustment factors, the HCM 2000 Urban Street Worksheet is provided <br /> because it lists additional factors which influence capacity, such as Arrival Type and Urban Street <br /> Class. See Exhibit 3. <br /> NOTE: Two-way daily capacity = One-way hourly capacity/K /D. <br /> The following equation is used to estimate the hourly one-way ultimate capacity (LOS E) of <br /> arterials and collectors. <br /> c = so*N*fW*fHV*fg*fp*fbb*fa*fLu*fLT*fRT*fLpb*fRpb*PHF*g/C <br /> Where <br /> c = Capacity (veh/hr), by direction. <br /> so = Base saturation flow rate —the maximum steady traffic flow rate for a signalized <br /> intersection approach in pc/hr/In under ideal conditions, assuming all green time is <br /> available & no lost time is experienced. HCM 2000, p. 10-24, Exhibit 10-12. <br /> 1,900 pc/hr/In assumed for arterials <br /> 1,805 pc/hr/In assumed for collectors/locals <br /> N = Number of useable through lanes at the intersection approach per direction (excludes <br /> exclusive turn lanes, or lanes assumed unusable due to parking, transit operations, etc.) <br /> PHF = Peak-hour factor. Default = 0.92, HCM 2000, p. 10-8 <br /> g/C = Effective green ratio, or the proportion of effective green time available to a given <br /> approach. Larger ratios are associated with higher volume/priority facilities. <br /> See Exhibit 2 for other adjustment factors for urban streets <br /> For NCDOT— TPB Level of Service D for Systems Level Planning, the NCLOS 2.1 program was <br /> used in developing the boulevard, major thoroughfares, and minor thoroughfares capacity tables. <br /> D-1 <br />