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Dowling Associates, Inc. <br />Transportation Engineering • Planning• Research• Education <br />Existing+Approved Levels of Service <br />Level of Service is a qualitative indication of the level of delay and congestion <br />experienced by motorists using an intersection. Levels of service are designated by <br />the letters A through F, with A being the best conditions and F being the worst (in <br />terms of congestion and delay). LOS A, B, C and D are considered to have <br />congestion levels in the acceptable range, while LOS E and F are considered <br />unacceptable. <br />The levels of service at the signalized intersections are evaluated using the HCM <br />signal operations method, based on City standards. The LOS calculation <br />methodology provides a single delay value and the resultant level of service for the <br />intersection as a whole. The method determines an average control delay per <br />intersection for the intersection. The delay criteria for signalized intersection levels <br />of service are shown in Table 1. <br />Table 1 <br />Level of Service Criteria <br />Signalized Intersections <br />Level of Average <br />Service Vehicle <br />(LOS) Control Description <br />Delay <br />{Seconds) <br />A < 10.0 Free Flow/Insignificant Delays: No approach phase is fully utilized <br />by traffic and no vehicle waits longer than one red indication. <br />B 10.1-20.0 Stable Operation/Minimal Delays: An occasional approach phase is <br />fully utilized. Many drivers begin to feel somewhat restricted within <br />platoons of vehicles. <br />C 20.1-35.0 Stable Operation/Acceptable Delays: Major approach phases fully <br />utilized. Most drivers feel somewhat restricted. <br />D 35.1-55.0 Approaching Unstable/Tolerable Delays: Drivers may have to wait <br />through more than one red signal indication. Queues may develop but <br />dissipate rapidly, without excessive delays. <br />E 55.1-80.0 Unstable Operation/Significant Delays: Volumes at or near capacity. <br />Vehicles may wait through several signal cycles. Long queues form <br />upstream from intersection. <br />F • 80 Forced Flow/Eacessive Delays: Represents jammed conditions. <br />Intersection operates below capacity with low volumes. Queues may <br />block upstream intersections. <br />Source: Transportation Research Boazd, "Highway Capacity Manual,' 2000 <br />Traffrc Analysis Page 5 <br />Ruby Hill Conversion, Pleasanton <br />