5.2. SR 08-08-2011 - Laserfiche WebLink

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i~ i~ i~ i~ ii Table 21- 2 -Intersection Level of Service Ranges A . • ~ -; <_ 10 1• • ~ •, <_ 10 B 10 -20 10 -15 C 20 -35 15 -25 D 35 - 55 25 - 35 E 55 -80 35 -50 F >80 >50 Source: HCM ' LOS, as described above, can also be determined for the individual legs (sometimes referred to as "approaches") or lanes (turn lanes in particular) of an intersection. It should be noted that a LOS E or F might be acceptable or justified in those cases where a leg(s) or lane(s) has a very low traffic volume as compared to the volume on the other legs. For example, improving LOS on such low-volume legs by converting a ' two-way STOP condition to an all-way stop, or adjusting timing at a signalized intersection, could result in a significant penalty for the many drivers on the major road while benefiting the few on the minor road. Also, geometric improvements on ' minor legs, such as additional lanes or longer turn lanes, could have limited positive effects and might be prohibitive in terms of benefit to cost. Although LOS A represents the best possible level of traffic flow, the cost to ' construct roadways and intersection to such a high standard often exceeds the benefit to the user. Funding availability might also lead to acceptance of intersection ' or roadway designs with a lower LOS. LOS D is generally accepted as the lowest acceptable level in urban areas. LOS C is often considered to be the desirable minimum level for rural areas. LOS D or E may be acceptable for limited durations or distances, or for very low-volume legs of some intersections. The LOS analysis for the 171St Avenue Area AUAR was performed using ' Synchro/SimTraffic: • Synchro, a software package that implements Highway Capacity Manual (HCM) methodologies, was used to build each signalized intersection and provide an input database for turning-movement volumes, lane geometrics, and signal design and timing characteristics. In addition, Synchro was used to optimize signal timing parameters for future conditions. Output from Synchro is ' transferred to SimTraffic, the traffic simulation model. • SimTraffic is amicro-simulation computer modeling software that simulates each individual vehicle's characteristics and driver behavior in response to traffic volumes, intersection configuration, and signal operations. The model simulates drivers' behaviors and responses to surrounding traffic flow as well as ' City of Elk River Draft Alternative Urban Areawide Review July 2011 Page 61 of 84