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HomeMy WebLinkAbout6_EX06_RS_Queuing Analysis_220201_v1 2813 Rockefeller Avenue  Suite B  Everett, WA 98201 Tel: 425-339-8266  Fax: 425-258-2922  E-mail: info@gibsontraffic.com Queuing Analysis Memorandum To: Nick Wecker, Senior Planner Barghausen Consulting Engineers, Inc. From: Brad Lincoln, PE Subject: Queuing Analysis Project: Renton Brown Bear Car Wash GTC #21-372 Date: January 31, 2022 Gibson Traffic Consultants, Inc. (GTC) has been requested to provide a queuing analysis for the Brown Bear Car Wash located at 800 Grady Way in the City of Renton. There is an existing tunnel car wash currently on the site, which also includes a gas station with convenience store and a self- serve car wash area. The current tunnel car wash has a single queue lane and capacity for 5 to 6 vehicles. There are currently traffic control devices on the site to help with the flow of vehicles into the tunnel car wash. It is therefore assumed that vehicles routinely queue beyond the marked crossing area and into the drive aisle. The proposal is to construct an Auto Sentry with two payment kiosks for the existing tunnel car wash to provide unattended, point-of-sale transactions. The proposal will not affect the operations of the tunnel car wash with regards to service capacity. However, there is a request for a reduced minimum setback for the Auto Sentry, which triggers the need for this analysis. 1. TRIP GENERATION The trip generation calculations for the existing Brown Bear Car Wash development have been performed using trip generation data contained in the Institute of Transportation Engineers’ (ITE) Trip Generation Manual, 11th Edition (2021). The average trip generation rates for ITE land Use Code (LUC) 948, Automated Car Wash, has been used to determine the weekday PM peak-hour trip generation of the existing car wash. ITE data shows a trip generation rate of 77.5 trips, 50% inbound and 50% outbound, per tunnel. This means the existing Brown Bear Car Wash generates approximately 80 weekday PM peak-hour trips. This equates to 40 vehicles per hour using the car wash. The trip generation data is included in the attachments. Brown Bear Car Wash Queuing Analysis Gibson Traffic Consultants, Inc. January 2022 info@gibsontraffic.com 2 GTC #21-372 2. ON-SITE QUEUING The existing Brown Bear Car Wash can service two vehicles at a time and is proposed to include space for a total of 8 vehicles between the drive aisle/marked crossing area and the car wash tunnel. This includes two vehicles at each of the payment kiosks (4 total vehicles) and 4 vehicles between the payment kiosks and the tunnel. The tunnel is able to serve 55 vehicles per hour based. The number of vehicles that are anticipated to be queued has been calculated using the service rate and anticipated arrival rate of 40 vehicles in an hour (based on the gross PM peak-hour trip generation of 78 vehicles). The calculations show that the 8 vehicles queued outside the tunnel equates to the 94th Percentile queue. It is important to note that the queue calculations account for only 1 vehicle in the tunnel at a time. Including a second vehicle would result in a theoretical queue of 9 vehicles. This equates to a 96th Percentile queue. This means that the additional payment kiosk and queuing area will provide for approximately the 95th Percentile queue length, meaning there is a 95% probability that the queue length will be within the provided area. The queues should therefore not significantly impact the operations of the site. 3. CONCLUSIONS The proposed Auto Sentry payment kiosks will increase the queuing area by approximately 60% (5 vehicles to 8 vehicles) and it anticipated to decrease the likelihood of vehicles impacting the drive aisle and marked crossing area. The Auto Sentry payment kiosks are anticipated to improve the operations of the site. A Attachments