2019-06-10-minutes-public-works-study-session

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KITTITAS COUNTY DEPARTMENT OF PUBLIC WORKS PUBLIC WORKS — BOARD OF COUNTY COMMISSIONERS STUDY SESSION STAFF REPORT STUDY SESSION DATE: June 10th, 2019 TOPIC: Speed Study Results for Thrall Road at Payne Road ACTION REQUESTED: Schedule a Public Hearing for July 02, 2019 at 2:00 PM Local Time Receiving the Results of the Thrall Road Speed Study at Payne Road LEAD STAFF: Mark R. Cook RECOMMENDATION: Schedule a public hearing for July 02, 2019 at 2:00 PM local time receiving the results of the Thrall Road speed study at Payne Road BRIEFING SUMMARY: • Payne Road resident requested speed study of Thrall Road at Payne Road • Study conducted 05-09-2019 through 05-16-2019 + 85th percentile speed is 54.5 MPH (posted 50 MPH) • Interim County Engineer requested supplemental sight distance investigation confirms road design geometries support 50 MPH BACKGROUND: There is a sight limiting vertical curve on Thrall Road east of the Payne Road intersection. Residents report that traffic exiting Payne Road onto Thrall is constantly required to aggressively accelerate onto Thrall Road owing to oncoming traffic cresting over the vertical curve westbound. DISCUSSION: Our speed study affirms that the traveling public is driving roadway geometries in a manner slightly exceeding the posted speed. The exceedance is approximately 5 MPH at the 85' percentile. Public Works (PW) conducted a supplementary sight distance evaluation (EXHIBIT 1) and confirmed that 550 feet of stopping sight distance is available from Payne Road which is the required distance by acceptable national standard. Traffic traveling 55 MPH over the crest vertical curve on Thrall Road requires 610 feet of safe stopping sight distance. Vehicles exceeding the posted speed at this location create a potentially unsafe condition for traffic exiting Payne Road onto Thrall Road. Page 1 of 4 PUBLIC WORKS BOARD OF COUNTY COMMISSIONERS WORK SESSION STAFF REPORT