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For each intersection analyzed the average control delay per vehicle per approach is determined for the peak hour. A weighted average of control delay per vehicle is then determined for the intersection. A LOS designation is given to the control delay to better describe the level of operation. A description of levels of service for signalized intersections can be found in Table A-V Table A-V: Description of Level of Service for Signalized Intersections LOS Description Very low Control delay, up to 10 seconds per vehicle. Progression is extremely favorable, and most A vehicles arrive during the green phase. Many vehicles do not stop at all. Shoff gcle lengths may tend to contribute to low delay values. 8 Control delay greater than 10 and up to 20 seconds per vehicle. There is good progression or short cycle lengths or both. More vehicles stop causing higher levels of delay. Control delay greater than 20 and up to 35 seconds per vehicle. Higher delays are caused by fair C progression or longer cycle lengths or both. Individual Lytle failures may begin to appear. Cycle failure occurs when a given green phaze doe not serve queued vehicles, and overflow occurs. The number of vehicles stopping is significant, though many still pass through the intersection without stopping. Control delay greater than 35 and up to 55 seconds per vehicle. The influence of congestions becomes D more noticeable. Longer delays may result from some combination of unfavorable progression, long cycle lengths, or high volumes. Many vehicles stop, the propottion of vehicles not stopping declines. Individual cycle failures are noticeable. Control delay greater than 55 and up to 80 seconds per vehicle. The limit of acceptable delay. High E delays usually indicate poor progression, long cycle lengths, and high volumes. Individual gcle failures are frequent. Control delay in excess of 80 seconds per vehicle. Unacceptable to most drivers. Oversaturation, arrival P flow rates exceed the capacity of the intersection. Many individual cycle failures. Poor progression and long cycle lengths may also be contributing factors to higher delay. Source: Highway Capacity Manual 2000 The use of control delay, which may also be referred to as signal delay, was introduced in the 1997 update to the Highway Capacity Manual, and represents a departure from previous updates. In the third edition, published in 1985 and the 1994 update to the third edition, delay only included stopped delay. Thus, the LOS criteria listed in Table A-V differs from earlier criteria. Unsignalized Intersections The current procedures on unsignalized intersections were first introduced in the 1997 update to the Highway Capacity Manual and represent a revision of the methodology published in the 1994 update to the 1985 Highway Capacity Manual. The revised procedures use control delay as a measure of effectiveness to determine LOS. Delay is a measure of driver discomfort, frustration, fuel consumption, and increased travel time. The delay experienced by a motorist is made up of a number of factors that relate to control, traffic and incidenu. Total delay is the difference between the travel time actually experienced and the reference travel time that would result during base conditions, i, e., in the absence of traffic control, geometric delay, any incidents, and any other vehicles. Control delay is the increased time of travel for a vehicle approaching and passing through an unsignalized intersection, compared with a free-Flow vehicle if it were not required to slow or stop at the intersection.