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Item 7B - Traffic Impact Analysis - 06-09-2021TRAFFIC IMPACT GROUP, LLC TO: Clay Cristy, P.E., ClayMoore Engineering FROM: Scott Israelson, P.E., PTOE DATE: 9 June 2021 RE: Drive -Through Queue Analysis NW Corner of Southlake Et White Chapel Southlake, TX Introduction Phillips Edison $ Co proposes to redevelop a site in Southlake, Texas. The site is located in the northwest corner of Southlake Boulevard Et White Chapel Road and is currently occupied by a gas station. The redevelopment proposes to construct a building totaling 4,600 SF. Vehicles will access the site using existing driveways to the commercial area. The planned uses are a 2,500 SF retail site and a 2,100 SF restaurant with drive -through window. Although no tenants are planned yet, it is probable that the restaurant will be a coffee shop. The site plan is attached. The City of Southlake requested this analysis to determine if the drive -through window is feasible with respect to queueing. Trip Generation This analysis uses the ITE Trip Generation Manual 10th Edition to estimate the projected trips by coffee shop portion of development. Table 1 contains the summary of the trip generation estimate. www.traffic-impact.com 1432 Greenway Drive, Suite 800, Irving, TX 75038 11 P a g e TRAFFIC IMPACT GROUP, LLC Queueing Analysis Queue analysis for entrance gate examines two key factors; arrival flow rate, and departure flow rate. The arrival flow rate, A, is measured by the expected entering trips generated by the development in the peak hour. For this project, the AM peak is the highest hour, and the expected number of entering vehicles is 95 vehicles per hour. According to the ITE Trip Generation Handbook, fast-food restaurants experience a pass -by rate between 32% and 68% percent in the AM peak hour. Pass -by rates can be used to assume the number of entering trips that use the drive -through window. The trip generation estimates an entering volume is 95 vph in the peak hour. This analysis assumes 50% of entering volumes will use the drive -through window, so the arrival flow rate is 47 vph. The departure flow rate, p, is based on the average service time for a vehicle to order and receive the coffee. According to experience, the processing rate is one minute per order, providing that vehicles are directed to exit the drive -through lane and park for orders that take longer than one minute. The departure flow rate is 60 vph. Estimating how many vehicles are in a queue uses the relationship between the two rates. The mean queue length is calculated by the following equation: E. = A2 / p * (p-A) The mean queue length at the pickup window is expected to be 472 / (60 * (60 - 47)), or 2.83 vehicles. The probability of more than N vehicles in a queue is calculated by the following equation: P(n>N)=(A/p)"'' To determine how often there will be more than one vehicle in the queue, we find that P(n > 1) = (47 / 60) 2, or 0.614. This means 61.4% of queues will be greater than one vehicle. Using that formula to achieve the 95th percentile, analysis shows that 94.7% of queues will be eleven cars or less. Therefore, the amount of queue storage should provide room for eleven vehicles. The calculations are attached to this memo. www.traffic-impact.com 1432 Greenway Drive, Suite 800, Irving, TX 75038 2 1 P a g e I I �.. 30'BUILDING SETBACK / PROPERTY LINE R3, 101ANDSCAPE BUFFER op 120�T0 OR4ERPOINT ' w. / 4,600 SF BUILDING 1.08 ACRES i r 35 PARKING SPACE (2 A©A} • I ----- - zs. • s _ �_ __ _ '• Pao Rio c 1 r PATIO �. k ir. m r m0 N _ A T T m \ � r m I SOUTHLAKE BLVD. (FM 1709) G - 0 V O Q _ 1 n a � ; 1 GRAPHIC SCALE 20 0 10 20 40 1 inch = 40 ft. PARKING TABLE PARKING REQUIRED 2,100 SF REST. - 1/100 35 SPACES (2 ADA) 100 SF PATIO - 1/100 2,500 RETAIL - 1/200 PARKING PROVIDED 35 SPACES (2 ADA) EXISTING PARKING 349 SPACES OVERALL LOT TO REMAIN OVERALL SITE PLAN SCALE 1-.100 CJ z wLLJ a z z L1J P R E L I M I N A R Y FORREVIEW ONLY Not for a t—ti- purposes. OLAYMOORE ENGINEERING CLAY CRISTY _ .109800 o e 8/2/2021 'A T� A�v W � �x ax~� xo � a� C-1 6-022 SIMPLE Drive Through Queueing Arrival Rate 47 vph Departure Rate 60 vph Mean Queue P7ql vehicles Mean Queue length Feet Probablility of more than 11 vehicles Probabilty is 5.3%