Vantage Bay PUD Final Development Plan Index Master File

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Vantage Bay PUD Updated Traffic Impact Study TENW September 1, 2017 Page 3 Project Trip Distribution The distribution of project generated trips were based on the proposed developments location in relationship to the I-90 on/off ramps. The proposed site is located less than one mile south of the I-90 ramps; therefore 90 percent of the project trips were assumed to/from the north on Huntzinger Road and 10 percent of the project trips were assumed to/from the south. Turn Lane Assessment The need for right and left-turn lanes along the project frontage on Huntzinger Road was assessed based on guidelines included in the Washington State Department of Transportation (WSDOT) Design Manual. Existing 2017 Average Daily Traffic (ADT) volumes on Huntzinger Road were based on a 2017 ADT count provided by Kittitas County (444 vehicles). Based on a comparison of historic volumes on Huntzinger Road, it was determined that the average annual growth rate on Huntzinger Road is less than one percent. Conservatively, a one percent annual growth rate was used to estimate future 2019 ADT volumes on Huntzinger Road. As a result, future 2019 ADT volumes on Huntzinger Road were estimated to be 453 vehicles (444 X 1.01^2). Right-Turn Lanes on Huntzinger Road The need for right-turn lanes on Huntzinger Road were assessed based on WSDOT Design Manual exhibit 1310-11 (see Attachment C). As shown in exhibit 1310-11, a minimum of 25 peak hour right-turns are needed before a right-turn pocket/taper or lane would be considered. The estimated number of Saturday peak hour northbound right-turns on Huntzinger Road entering the proposed site is 11 vehicles (10% of 114 entering trips). Assuming all right-turning vehicles enter the site using only one of the two proposed accesses on Huntzinger Road, a right-turn pocket/taper or lane would still not be recommended based on WSDOT standards. Left-Turn Lanes on Huntzinger Road The need for left-turn lanes on Huntzinger Road were assessed based on WSDOT Design Manual exhibit 1310-7a (see Attachment C). The estimated number of Saturday peak hour southbound left-turns on Huntzinger Road entering the site is 103 vehicles (90% of 114 entering trips). Based on exhibit 1310-7a and a 50 mph posted speed, 300 peak hour thru vehicles (total of both directions) would be needed on Huntzinger Road before a left-turn lane would be needed for capacity (300 thru vehicles equates to a total design hour volume (DHV) of 414 vehicles: 300 background thru trips + 103 project generated southbound lefts + 11 project generated northbound rights). Based on the estimated 2019 ADT of 453 vehicles on Huntzinger Road, it is unlikely that approximately 300 thru trips (2/3 of the ADT) would occur during the peak hour of the proposed development. Therefore, a left- turn lane on Huntzinger Road would not be recommended based on WSDOT guidelines. Index #5