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37 Snoqualmie Pass Comprehensive Safety Plan I Kittitas County Level of Service Level of Service (LOS) is a metric used to assess how well intersections function by evaluating tactors such as vehicle delay, congestion, and overall traffic flow. It provides a snapshot of operational performance during periods of high demand. Due to the unique traffic patterns in Snoqualmie Pass, intersection performance was analyzed during peak hours on both weekdays and weekends. To capture seasonal variation, data collection was conducted in October, reflecting traffic during non- snow conditions, and in February reflecting traffic during the ski season. The LOS grading system ranges from A to F, with each grade representing a different level of congestion. An intersection operating at LOS A signifies a smooth flow of traffic with minimal or no delays. On the other hand, an intersection operating at LOS F indicates severe congestion, causing significant delays for vehicles and exceeding the roadway's capacity. Table 1 presents the definitions of each LOS grade for unsignalized intersections- as established in the Highway Capacity Manual (HCM) 7th Edition and published by the Transportation Research Board in 2o22.fhe HCM serves as a standardized approach for evaluating vehicle operations. WSDOT establishes LOS standards for state highways and ferry routes of statewide significance (HSS) under RCW 47.06.14O(2).For SR 905, WSDOT has identified an LOS C standard.t Kittitas County's 2021 Comprehensive Plan sets LOS standards for its roadway network based on geographic context. The County aims to maintain LOS C in rural areas and LOS D in urban areas, with Snoqualmie Pass classified as a rural area.+ Based on the traffic counts collected and current intersection geometries, all intersections within the study area operated at LOS A or B during peak hours in October (representing non-snow conditions). ln February, which captures ski season travel patterns and increased weekend congestion, most intersections still operated at LOS B or better. Only SR 905 & l-90 EB Off-Ramp dropped to LOS C on weekends, still within the acceptable standard set by WSDOT. These results do not apply to all time periods. The study area's roadway network is relatively sparse, offering limited route options for most travelers. As a result, the area roadway network can be overwhelmed in the mornings as people arrive to park for their day of winter sports, as well as in the afternoon, as people leave for the day. The rural network accommodates a mix of through traffic, cars searching for a place to park, vehicles parking, people walking from parked vehicles to destinations, semi-trucks stopping to rest or access services, and travelers that are unfamiliar with the area, who sometimes make unpredictable or even unsafe travel maneuvers. The friction that occurs during these busy periods can impact safety and mobility, as well as quality of life, particularly for those who live and work in the Pass. ln addition to considering current conditions, the project team Table 1. Level of Service Definitions A B c D E F Free-fl owing conditions Stable operating conditions Stable operating conditions, but individual motorists are affected by the interaction with other motorists High density of motorists, but stable flow Near-capacity Over capacity, with delays s10 10-15 15-25 25-35 35-50 >50 Source: Highway Capacity Manual, 7th Edition. . AllintersectionsinSnoqualmiePassareunsignalizedintersections.TheHCMhasadifferentdelaystandardforsignalizedandroundaboutcontrolledintersections. t httTs://seowa-eov/d.tasets/WSDOT::wsdot-level-of-servi.e-stan.l:rd-for-st2te-routes/exnlore?location=47-4169O3oln2C-1'1417?23olnaC14-55 f https://www.co.kittilaswa.rrs/unloads/documents/cds/comn-olan/2021l2021%20Comorehensive%20Plan.odf Level of Service Description Control Delay (seconds/vehicle) for Unsignalized lntersections The following intersections were evaluated (as shown inFigure22)z . SR 906 & l-90 EB Off Ramp (Location 1) . SR 906 & Guye Peak Lane (Location 2) . l-90 WB Off Ramp/l-9O WB On Ramp & Yellowstone Trail Road (Location 4) . SR 906 & Tanner Way/Driveway (Location 6) . Hyak Dr E & SR 906 & Driveway (Location 7) . SR 906 & l-90 EB Off Ramp/l-9O EB On Ramp (Location 8) . SR 906 & l-90 WB Ramp (Location 9)