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1/11/2001 APPENDIX TABLE 1 LEVEL OF SERVICE CRITERIA-FOR SIGNALIZED,UNSIGNALIZED,AND ALL-WAY-STOP CONTROLLED INTERSECTIONS LEVEL OF CONTROL DELAY[VEHICLE(SEC) SERVICF TYPE OF FLOW DELAY MANEUVERABILITY SIGNALIZED UNSIGNALIZED ALL-WAY STOP A Stable Flow Very slight delay. Progression is very favorable, with Turning movements are easily r` <,110'0 t . < 10.0 < 10.0 most vehicles arriving during the green phase not stopping made,and nearly all drivers .ak� c ` �j tx��r, e" at all. find freedom of operation. #� `� B Stable Flow Good progression and/or short cycle lengths. More Vehicle platoons are formed. >10 and < >10 and < 15.0 >10 and < vehicles stop than for LOS A, causing higher levels of Many drivers begin to feel 20.0 15.0 average delay, somewhat restricted within groups of vehicles. C Stable Flow Higher delays resulting from fair progression and/or Back-ups may develop behind >20 and < >15 and < 25.0 >15 and < longer cycle lengths. Individual cycle failures may begin turning vehicles. Most drivers L 35.0 25.0 to appear at this level. The number of vehicles stopping feel somewhat restricted s significant, although many still pass through the Intersection without stopping. D Approaching The influence of congestion becomes more noticeable. Maneuverability is severely >35 and < >25 and < 35.0 >25 and < Unstable Flow Longer delays may result from some combination of limited during short periods 55.0 35.0 unfavorable progression, long cycle lengths,or high due to temporary back-ups. volume-to-capacity ratios. Many vehicles stop, and the proportion of vehicles not stopping declines. Individual cycle failures are noticeable. E Unstable Flow Generally considered to be the limit of acceptable delay. There are typically long queues >55 and < >35 and < 50.0 >35 and < Indicative of poor progression, long cycle lengths, and of vehicles waiting upstream of 80.0 50.0 high volume-to-capacity ratios. Individual cycle failures the intersection. are frequentoccur rences. Forced Flow Generally considered to be unacceptable to most drivers. Jammed conditions. Back-ups > 80.0 > 50.0 > 50.0 Often occurs with over saturation. May also occur at from other locations restrict or high volume-to-capacity ratios. There are many prevent movement. Volumes individual cycle failures. Poor progression and long cycle may vary widely, depending lengths may also be major contributing factors. principally on the downstream back-up conditions. References: Highway Capacity Manual, Special Report No. 209, Transportation Research Board, Updated December]997. 7 2237 Douglas Boulevard, Suite 100, Roseville, CA 95661 -(916)782-8688 fax(916)782-8689