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T RAFFIC I MPACT A NALYSIS <br />S EPTEMBER 2017 <br />C HRIST O UR S AVIOR C ATHOLIC P ARISH <br />S ANTA A NA , O RANGE C OUNTY , C ALIFORNIA <br /> <br />P:\DOM1701\doc\Traffic Impact Analysis.docx «09/20/17» 7 <br />LOS Description <br />A No approach phase is fully utilized by traffic, and no vehicle waits longer than one red indication. Typically, the <br />approach appears quite open, turns are made easily, and nearly all drivers find freedom of operation. <br />B This service level represents stable operation, where an occasional approach phase is fully utilized, and a <br />substantial number are nearing full use. Many drivers begin to feel restricted within platoons of vehicles. <br />C This level still represents stable operating conditions. Occasionally, drivers may have to wait through more <br />than one red signal indication, and backups may develop behind turning vehicles. Most drivers feel somewhat <br />restricted, but not objectionably so. <br />D This level encompasses a zone of increasing restriction approaching instability at the intersection. Delays to <br />approaching vehicles may be substantial during short peaks within the peak period; however, enough cycles <br />with lower demand occur to permit periodic clearance of developing queues, thus preventing excessive <br />backups. <br />E Capacity occurs at the upper end of this service level. It represents the most vehicles that any particular <br />intersection approach can accommodate. Full utilization of every signal cycle is attained no matter how great <br />the demand. <br />F This level describes forced flow operations at low speeds, where volumes exceed capacity. These conditions <br />usually result from queues of vehicles backing up from a restriction downstream. Speeds are reduced <br />substantially, and stoppages may occur for short or long periods of time due to the congestion. In the extreme <br />case, speed can drop to zero. <br />LOS = level of service <br /> <br />The relationship between LOS and the ICU value (i.e., the v/c ratio) is as follows: <br />Level of Service Intersection Capacity Utilization <br />A < 0.60 <br />B 0.61–0.70 <br />C 0.71–0.80 <br />D 0.81–0.90 <br />E 0.91–1.00 <br />F > 1.00 <br /> <br />The relationship between LOS and the HCM delay (at unsignalized intersections) is as follows: <br />Level of Service Unsignalized Intersection Delay per <br />Vehicle (seconds) <br />A < 10.0 <br />B 10.0–15.0 <br />C 15.0–25.0 <br />D 25.0–35.0 <br />E 35.0–50.0 <br />F > 50.0 <br /> <br />The City considers LOS D to be the upper limit of satisfactory operations. Mitigation is required for <br />any intersection where project traffic causes the intersection to deteriorate from LOS D to LOS E <br />or F. <br />3-58