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KITTITAS COUNTY <br />DEPARTMENT OF PUBLIC WORKS <br />PUBLIC WORKS — BOARD OF COUNTY COMMISSIONERS <br />ENGINEER'S REPORT — UMPTANUM ROAD SPEED LIMIT REDUCTION <br />REQUEST <br />PUBLIC HEARING DATE FEBRUARY 19, 2019 <br />ACTION REQUESTED CONSIDER REDUCING THE POSTED <br />SPEED FROM 50 MPH TO 35 MPH <br />LEAD STAFF: Mark R. Cook, Public Works Director/County Engineer <br />RECOMMENDATION: <br />Maintain the existing speed along Umptanum Road from MP 0.75 to MP 2.68. <br />BACKGROUND: <br />Currently the speed limit along Umptanum Road from MP 0.75 to Riverbottom Road (MP 2.68) is 50 <br />MPH, at which it transitions to 35 MPH. Two county residents requested a speed reduction in this <br />road segment in October 2018 (EXHIBIT 1). Public Works staff conducted a speed study in late fall <br />of 2018 and recently produced results of the study for evaluation (EXHIBIT 2). <br />DISCUSSION: <br />A variety of factors must be considered when determining safe and reasonable speed limits. <br />The prevailing speed is a major consideration in setting speed limits. Engineers recommend <br />setting speed limits so that 85% of the freely flowing traffic travels at or below that speed (the <br />85th percentile). Guidance is provided in MUTCD 2B.13 (EXHIBIT 3), recommending posted <br />speed limits to be set "within 5 mph of the 85th percentile speed of free-flowing traffic." <br />Another consideration is the highest safe speed for which the road was designed. This takes <br />into account road type, road geometry, and adjacent land use. Other factors include presence <br />of non -vehicular road users, driver or vehicle characteristics, enforcement capability, and <br />public attitudes. <br />The requested speed reduction along Umptanum Road (MP 0.75 to MP 2.68) does not appear to be <br />supported by the results of the speed study. Umptanum drivers are generally doing the posted speed <br />(49.5, 49.2 and 51.2 MPH). Drivers along Manastash are exceeding at MP 0.0 to MP 0.74 (56/50 <br />MPH). Riverbottom drivers are matching the posted 35 MPH speed MP 0.0 to 1.83: (33.2/35 MPH) <br />and MP 1.83 to 3.06: (34.5/35 MPH). The vast majority of drivers are driving at the 85th percentile or <br />within 5 MPH of the speed of free flowing traffic. <br />Several property damage accidents along Umptanum Road have occurred since 2015: 9 citing various <br />reasons (EXHIBIT 2). Two injury accidents along Manastash Road citing inattention have occurred in <br />the same time period. Two property damage accidents along Riverbottom Road have taken place <br />owing to "unknown driver distraction". <br />Page 1 of 5 <br />PUBLIC WORKS BOARD OF COUNTY COMMISSIONERS ENGINEER'S REPORT <br />