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Figure T-5 <br /> Level of Service for Urban and Suburban Arterial Streets <br /> V/C <br /> LOS Description Ration <br /> A Free Flow. Very slight or no delay. If signalized, 0.00 - 0.60 <br /> conditions are such that no approach phase is fully <br /> utilized by traffic, and no vehicle waits longer <br /> than one red indication. Turning movements are <br /> easily made, and nearly all drivers find freedom <br /> of operation. <br /> B Stable Flow. Slight delay. If signalized, an occa- 0.61 - 0.70 <br /> sional approach phase is fully utilized, vehicle <br /> platoons are formed. Many drivers begin to feel <br /> somewhat restricted within groups of vehicles. <br /> This level is suitable operation for rural design <br /> purposes. <br /> C Stable Flow. Acceptable delay. If signalized, a few 0.71 - 0.80 <br /> drivers arriving at the end of a queue may occasionally <br /> have to wait through one signal cycle. Backups may <br /> develop behind turning vehicles. Most drivers feel <br /> somewhat restricted. <br /> D Approaching Unstable Flow. Tolerable delay. Delays may 0.81 - 0.90 <br /> be substantial during short periods, but excessive <br /> backups do not occur. Maneuverability is severely <br /> limited during short periods due to temporary backups. <br /> E Unstable Flow. Intolerable delay. Delay may be great, 0.91 - 1.00 <br /> up to several signal cycles. There are typically long <br /> queues of vehicles waiting upstream of the intersection. <br /> F Forced Flow. Excessive delay. Intersection operates Varies <br /> below capacity. Jammed conditions. Backups from other <br /> locations restrict or prevent movement. Volumes may <br /> vary widely, depending principally on the downstream <br /> backup conditions. <br /> Source: Transportation Research Board 1985. <br /> a V/C ratios cannot bereater than 1.00 unless the lane capacity tions are too low. <br /> g P Y assum P <br /> If future demand projections are considered for analytical purposes, a ratio greater than <br /> 1.00 might be obtained, indicating that the projected demand would exceed the capacity. <br /> 41 <br />