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'A <br />The intersection capacity analysis involved a transportation <br />a <br />planning approach. The number of arterial lanes required to accommodate <br />the directional design hourly volume (DDHV) was determined. <br />i� <br />The High Flow Arterial Concept Feasibility Study completed by <br />the Orange County Transportation Commission examined several high volume <br />r. <br />intersections in Orange County. The study disclosed that 70-80 percent <br />of traffic approaching a signalized intersection is thru traffic which <br />receive 35-40 percent of the green time. <br />!> From this information, an intersection capacity was estimated <br />( for thru and right turn traffic. This capacity is based on actual <br />i <br />experience at Main/La Veta where flow rates equivalent to 1,700 vehicles <br />(., per lane per hour of green were observed. A theoretical approach <br />capacity of 750-800 vplph was used in conjunction with SATC/TSIP Model <br />forecasts of the DDHV to predict intersection capacity. <br />Table 15 presents results of arterial capacity analysis <br />showing the forecasted DOW compared with the current peak hour volume <br />and the number of arterial lanes required to satisfy the demand. In the <br />case of Main Street and La Veta Avenue, a curiosity is noted with <br />r <br />respect to a significant difference in the directionality of the DDHV <br />flows. This situation is partially created by the construction of a new <br />l off -ramp directly into Fashion Square which eliminates the necessity to <br />!_ use Main Street northbound from the Santa Ana Freeway. A similar <br />situation occurs on La Veta Avenue where inbound traffic from the <br />1� southbound Santa Ana Freeway can use eastbound La Veta Avenue (from <br />Bristol/La Veta off -ramp) and return using eastbound La Veta Avenue to <br />the La Veta Avenue on -ramp. <br />In addition to the arterial lane requirements shown in Table <br />1� <br />! 15, a center median is recommended on Main Street with sufficient width <br />to accommodate dual left turn lanes and a future mass transit guideway. <br />The capacity analysis for Main Street indicates something less than-8 <br />lanes may be sufficient to satisfy thru traffic requirements, but it is <br />i <br />75D-241 <br />