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LEVEL OF SERVICE CONCEPT Signalized Intersection Level of Service (LOS) is the primary indicator for traffic operation performance at intersections. The volume-capacity ratio (v/c) is determined by the volume of conflicting traffic movements per hour and the capacity designed to accommodate them. This ratio, in turn, is rated from LOS "A" to "F." The range describes increasing traffic demand, delays, and deterioration of services. LOS "A" represents free-flow conditions with little or no delay (zero to five seconds) at intersections. On the contrary, LOS "E" characterizes extremely unstable flow conditions with volumes at or near the designed capacity. Vehicles are likely to experience major delays (40 to 60 seconds) crossing an intersection. Minor incidents may lead to forced flow conditions (LOS "F") with operating volume substantially below capacity. This results in long queues backing up from all approaches to intersections. LOS ratings from signalized and unsignalized intersections are determined based on different criteria and hence are not directly comparable. Two-Way Stop-Sign Controlled Intersection Level of service to individual turning movements on all approaches are determined by a number of factors. These include merging and opposing volumes, arrival frequency on the minor approach. approach speeds, critical gap, sign control, design capacity and intersection geometry. The resulting LOS reflects delays experienced by that minor street traffic. Thus, while the overall operating condition of the intersection is stable (LOS "C"), certain turning movements to/from the side street could experience delays equivalent to LOS "E" or "F." Four-Way Stop-Sign Controlled Intersection Vehicle delay is not related to critical gap since stopping is required on all approaches. Instead. interaction of vehicles is complex and depends on the arrival distribution on different approaches. departure headways, design capacity and intersection geometry. The resulting LOS reflects similar overall delays described for signalized locations. However, if volumes are substantially"unbalanced" between the intersection legs, vehicles on the highest volume approach would experience disproportionate delays.