Agenda - 11-19-2013 - 5c - Laserfiche WebLink

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29 Draft 11-19-2013 Traffic Level of Service (LOS) Average Daily Traffic relates directly to a concept called "Level of Service" (LOS). LOS is a measure used by traffic engineers to determine the effectiveness of elements of transportation infrastructure. LOS is most commonly used to analyze highways by categorizing traffic flow with corresponding safe driving conditions. LOS calculations attempt to describe the traffic conditions of a given roadway as it relates to the carrying capacity of the road. The following are descriptions of LOS: Level of Service Description of Operating Condition A Free flow. Individual users are virtually unaffected by the presence of others in the traffic stream. Freedom to select desired speeds and maneuver within the traffic stream is extremely high (< 10.0 second delay per vehicle). B Stable flow but the presence of other users in the traffic stream begins to be noticed. Freedom to select desired speeds is relatively unaffected, but there is a slight decline in the freedom to maneuver within the traffic stream (10.0-15.0 second delay per vehicle). C Stable flow but marks the beginning of the range in flow in which the operation of individual users becomes significantly affected by interactions with others in the traffic stream. Selection of speed affected and maneuvering within the traffic stream requires substantial vigilance on the part of the user (15.1-25.0 second delay per vehicle). D High-density but stable flow. Speed and freedom to maneuver are severely restricted. Small increases in traffic flow will generally cause operational problems at this level (25.1 to 35.0 second delay per vehicle). E Operating conditions at or near the capacity level. Speeds are reduced to a low, but relatively uniform level. Freedom to maneuver within the traffic stream is extremely difficult (35.1 to 20.0 second delay per vehicle). F Forced or breakdown flow. In the extreme, speed can be reduced to zero (Delay in excess of 50.0 seconds per vehicle). Source: Highway Capacity Manual, Transportation Research Board, 2010. For reference, many municipal governments adopt policies requiring that new development not decrease LOS below level C or D. Whether Level C or D is chosen depends upon the individual policy decision of the local government and/or the jurisdiction having maintenance control. In North Carolina, municipalities maintain roads but counties, such as Orange, do not. Determining the LOS for a given roadway involves complex calculations taking into account factors such as roadway grades and lane width. However, generalized tables have been developed to serve as a guide in determining LOS using Average Daily Traffic (ADT) counts. 171 Page