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~evel of Service Criteria <br />for Signalized Intersections <br /> <br />Level of <br />Service <br />Type of <br />Flow <br /> <br />Delay <br /> <br />Maneuverability Stopped <br />Delay/ <br />Vehicle <br />(sec) <br />•A Stable Very slight delay. Progression is Turning movements are easily <_ 5.0 <br /> Flow very favorable, with most made, and nearly all drivers <br /> vehicles arriving during the green find freedom of operation. <br /> phase and not stopping at all. <br />B Stable Good progression and/or short Vehicle platoons are formed. 5.1-15.0 <br /> Flow cycle lengths. More vehicles Many drivers begin to fee <br /> stop than for LOS A, causing somewhat restricted within <br /> higher levels of average delay. groups of vehicles. <br />C Stable Higher delays resulting from fair Back-ups may develop behind 15.1-25.0 <br /> Flow progression and/or longer cycle turning vehicles. Most <br /> lengths. Individual cycle failures drivers feel somewhat <br /> may begin to appear at this level. restricted. <br /> The number of vehicles stopping <br /> is significant, although many still <br /> pass through the intersection <br /> without stopping. <br />D Approaching The influence of congestion Maneuverability is severely 25.1-40.0 <br /> Unstable becomes more noticeable. limited during short periods <br /> Flow Longer delays may result from due to temporary back ups. <br /> some combination of unfavorable <br /> progression, long cycle lengths, <br /> or high volume-to-capacity ratios. <br /> Many vehicles stop, and the <br /> proportion of vehicles not <br /> stopping declines. Individual <br /> cycle failtures are noticeable. <br />E Unstable Generally considered to be the There are typically long 40.1-60.0 <br /> • Flow limit of acceptable delay. queues of vehicles waiting <br /> Indicative of poor progression, upstream of the intersection. <br /> long cycle lengths, and high <br /> volume-to-capacity ratios. <br /> Individual cycle failures are <br /> frequest occurrences. <br />F Forced Flow Generally considered to be Jammed conditions. Back > 60.0 <br /> unacceptable to most drivers. ups from other locations <br /> Often occurs with oversaturation. restrict or prevent movement. <br /> May also occur at high volume- Volumes may vary widely, <br /> to-capacity ratios. There are depending principally on the <br /> many individual cycle failures. downstream back-up <br /> Poor progression and long cycle conditions. <br /> lengths may also be major <br /> contributing factors. <br />References: Highway Capacity Manual, Special Report No. 209, Transporution Research Board, 1985. <br />Highway Capacity Manual, Special Report No. 87, Highway Research Board, 1965. (~ <br />TJKM. loll. b <br />