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3.3 Existing Traffic Volumes <br />Twenty-five (25) key study intersections have been identified as the locations at which to evaluate <br />existing and future traffic operating conditions. Some portion of potential project -related traffic will <br />pass through each of these intersections, and their analysis will reveal the expected relative impacts <br />of the project. These key locations were selected for evaluation based on discussions with City of <br />Santa Ana staff and in consideration of Orange County CMP requirements. <br />Existing daily, AM peak hour and PM peak hour traffic volumes for the twenty-five (25) key study <br />intersections evaluated in this report were obtained from manual turning movement counts <br />conducted by National Data and Surveying Services in May 2019. <br />Figures 3-5 and 3-6 illustrate the existing AM and PM peak hour traffic volumes at the twenty-five <br />(25) key study intersections evaluated in this report, respectively. Figure 3-6 also presents the <br />existing average daily traffic volumes for twelve (12) key roadway segments in the vicinity of the <br />proposed Project. Appendix B contains the detailed peak hour and daily traffic count sheets for the <br />key intersections and roadway segments evaluated in this report. <br />3.4 Existing Intersection Conditions <br />Existing AM and PM peak hour operating conditions for the twenty-five (25) key study intersections <br />were evaluated using the Intersection Capacity Utilization (ICU) methodology for signalized <br />intersections and the methodology outlined in the Highway Capacity Manual 6 (HCM 6) for <br />unsignalized intersections. <br />3.4.1 Intersection Capacity Utilization (ICU) Method of Analysis <br />In conformance with Cities of Santa Ana, Tustin and Orange County CMP requirements, existing <br />AM and PM peak hour operating conditions for the key signalized study intersections were <br />evaluated using the Intersection Capacity Utilization (ICU) method. The ICU technique is intended <br />for signalized intersection analysis and estimates the volume to capacity (V/C) relationship for an <br />intersection based on the individual V/C ratios for key conflicting traffic movements. The ICU <br />numerical value represents the percent signal (green) time, and thus capacity, required by existing <br />and/or future traffic. It should be noted that the ICU methodology assumes uniform traffic <br />distribution per intersection approach lane and optimal signal timing. <br />Per City of Santa Ana requirements, the ICU calculations use a lane capacity of 1,700 vehicles per <br />hour (vph) for through lanes and 1,600 vph for left -turn lanes and right -turn lanes. A clearance <br />adjustment factor of 0.05 was added to each Level of Service calculation. <br />Per City of Tustin requirements, the ICU calculations use a lane capacity of 1,700 for through and all <br />turn lanes. A clearance adjustment factor of 0.05 was added to each Level of Service calculation. <br />The ICU value translates to a Level of Service (LOS) estimate, which is a relative measure of the <br />intersection performance. The ICU value is the sum of the critical volume to capacity ratios at an <br />intersection; it is not intended to be indicative of the LOS of each of the individual turning <br />