Agenda - Public Works Committee - 10/19/2021

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I: i' Mr.Bruce Westby,PE r March 21,2017 Page 2 performedAM peak eak hour (6-9 am), mid-day (It-I pm), and PM peak hour (3-7 pm) turning movement traffic counts to determine typical weekday traffic patterns at this intersection. SEH also obtained crash data for the intersection for the 5 year period of 2011-2015 from the State's crash website. SEH then completed a brief field review of the signal system to confirm that the existingtraffic signal plans correspond to the current installation of the signal system and g take into account the current intersection geometrics. SEH also reviewed traffic signal cabinet components to determine if additional electrical equipment would be required to be provided in p order to allow for flashingyellow arrow operation to be used. I Y � E As part of the signal system installation, each intersection approach was set up to operate with protected left turn phasing (3-section RLA-YLA-GLA signals). The intersection has a newer Econolite ASC--3 controller unit and Reno MMU--1600-GE conflict monitor, both of which are fully compatible atible with upgraded left turn (i.e. flashing yellow arrow) operations. The controller pg �:- cabinet has sufficient load switch bays available to accommodate flashing yellow arrow operations. Thus, the existing controller and cabinet have the capacity and capability to p r; accommodate future flashing yellow arrow operations for all four intersection approaches without requiring this equipment to be significantly upgraded or revised. As Y art of our analysis, SEH utilized the Minnesota Department of Transportation's (MnDOT) p flashing yellow arrow installation criteria from their "Traffic Signal Timing and Coordination Manual" to analyze extended usage of flashing yellow arrow operations for each intersection approach. A copy of this criteria is attached for your information. Based on comparison of available data with the MnDOT criteria,the following can be inferred: The design of this signal system included the initial recommendation of protected left turn phasing for each intersection approach due to the higher posted speed limit of 55 m h on CSAH 83 (as is typical Anoka County practice) and the presence of a dual left p turn lane for the westbound Sunwood Drive approach. With regards to utilizing Flashing Yellow Arrow operations for each left turn movement, g g g the following should be noted: • According to the current edition of the AASHTO Geometric Design of Highways and Streets manual, left-turning drivers "need sufficient sight distance to decide when it is safe to turn left across the lanes used by opposing traffic." This stopping sight distance along CSAH 83 for the design/posted speed of 55 mph is at least 495 feet of clear sight distance to the north and south. For both Sunwood F Drive and 147th Avenue Northwest, the recommended stopping sight distance at 30 mph is as least 200 feet to the east and west. Based on a field review of intersection g eometrics, the southbound, eastbound, and westbound intersection approaches are straight for several hundred feet in each direction with no impediments to the sight distance (other than possible sun issues for eastbound F !r is ff f i r. I