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ANALYSIS OF NORTHBOUND LEFT TURN INTO ROSEDALE MARKET PLACE With a p.m. peak hour northbound left turn volume of 155 vehicles at a signalized south driveway, the key question to be answered is: WHAT IS THE MAXIMUM NUMBER OF VEHICLES THAT WILL BE ENTERING THE SITE IN ONE PLATOON, AND WILL IT AFFECT TRAFFIC ON FAIRVIEW AVENUE? The existing signal systems in the area now operate on a 90- second cycle length. Therefore, a typical cycle of the signal will release four northbound left -turning vehicles: (155 vehs/[3600 secs/go sec cycle]) = 4 veh/cycle Current Ramsey County practice is to provide Protected/permissive left turn signal operation. This type of operation provides a protected left turn- movement but also allows left turns to made on the through -street green interval, after they yield to oncoming traffic. Therefore, one or more left turns are typically mad e dur ing ng the through green interval or during the yellow time at the end of that interval. Those vehicles turning in gaps would therefore not be part of a larger platoon.. However, assuming that left turns are made only with the left turn arrow, the typical platoon will be 4 vehicles. For municipal and county type roadways, a factor of 1.5 times the average flow rate is often assumed for determining the "design" platoon size for design purposes. At this location, that would then be 4 vehicles times 1.5 = 6 vehicles per cycle for a standard maximum for design purposes. To ensure that the entrance performs adequately and well beyond nornally accepted levels of design, we have made the following further assumptions: (1) A factor of 2 times the average flow rate has been used rathe?_ than 1.5. This would produce a maximum platoon of 8 vehicles. (2) If Ramsey County were to increase the signal cycle length from 90 to 120 seconds, the combined effect of all of these possibilities would mean that the absolute maximum platoon Produced by the signal system would be 10 vehicles. Therefore, there will not be a ueuin c nomal .Lmstances with the three-way "Stop" controlbproposedrforrthe intersection at the end of the entrance. The storage of the maximum platoon will be an issue only if the FIRST vehicle of the 16