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3.2 Existing Traffic Volumes <br />Four (4) key study intersections and one (1) key roadway segment have been identified as the <br />locations at which to evaluate existing and future traffic operating conditions. Some portion of <br />potential project-related traffic will pass through each of these intersections, and their analysis will <br />reveal the expected relative impacts of the project. These key locations were selected for evaluation <br />based on discussions with City of Santa Ana staff and in consideration of Orange County CMP <br />requirements. <br />Existing daily, AM peak hour and PM peak hour traffic volumes for the key study intersections of <br />Tustin Avenue at Fourth Street and Tustin Avenue at First Street, as well as the one (1) key roadway <br />segment evaluated in this report were obtained from manual turning movement counts conducted by <br />Transportation Studies, Inc. in October 2016. Please note that counts collected in October 2016 were <br />grown by 1% to 2017 to create a 2017 baseline condition. <br />Existing AM peak hour and PM peak hour traffic volumes for the key study intersections of SR-55 <br />SB Ramps at Fourth Street and SR-55 NB Ramps at Fourth Street/Irvine Boulevard were obtained <br />from manual turning movement counts conducted by AimTD LLC in May 2017. <br />Figures 3-2 and 3-3 illustrate the existing AM and PM peak hour traffic volumes at the four (4) key <br />study intersections evaluated in this report, respectively. Figure 3-3 also presents the existing <br />average daily traffic volumes for the one (1) key roadway segment in the vicinity of the proposed <br />Project. Please note that these existing volumes include the traffic generated by the existing land <br />uses. Appendix B contains the detailed peak hour and daily traffic count sheets for the key <br />intersections and roadway segments evaluated in this report. <br />3.3 Intersection Analysis Methodologies <br />Existing AM and PM peak hour operating conditions for the four (4) key study intersections were <br />evaluated using the Intersection Capacity Utilization (ICU) methodology for signalized intersections <br />and the methodology outlined in the Highway Capacity Manual 6 (HCM 6) for the unsignalized <br />Project driveways. <br />3.3.1 Intersection Capacity Utilization (ICU) Method of Analysis <br />In conformance with City of Santa Ana, City of Tustin, and Orange County CMP requirements, <br />existing 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 />3-69