Agenda - Public Works Committee - 03/15/2022

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Mr. Bruce Westby, PE February 28, 2022 Page 3 Two (2) of the crashes were reported as either left turns into oncoming traffic or right angle crashes, with possible injuries noted for 1 of these crashes (listed as non -incapacitating). The right angle crashes were between southbound/eastbound through vehicles and between a southbound through vehicle and a northbound left turning vehicle. One of the 6 crashes was reported during morning hours (10-11 am), with the other 5 crashes being between 1-8 pm (1 crash during PM peak traffic period of 3-6 pm). Given the number and type of crashes recorded over the past 5 years of available crash data as well as analysis of the crash details, there does not appear to be any safety concerns at this intersection with the presence of signalized operation as concerns about right angle crashes are minor. • One of the recommendations from the MnDOT Traffic Signal Timing and Coordination Manual is to utilize protected left turn phasing only either for situations where the posted speed limit exceeds 45 mph and the peak hour left turning volume is greater than 240 vehicles per hour, or for when the cross product between left turn traffic volumes and the opposing through/right turning traffic volumes exceed 80,000 for one opposing through lane or exceeding 100,000 for two or more opposing lanes. This would translate to a left turn volume of 150 vehicles per hour with opposing traffic volumes between 500-700 vehicles per hour. For this analysis, we used the more conservative cross product of 80,000 in determining our recommendations for time of day flashing yellow arrow operation. Turning movement traffic count data (taken at the intersection by the City between January 26-27, 2022) was used in the flashing yellow arrow analysis. With regards to the available information: a. For northbound CSAH 56, the cross product between northbound left turns and southbound opposing traffic peaks at around 35,000 in the AM peak period (7-8 am) and around 30,000 in the PM peak period (4-5 pm). The highest hour of northbound left turning traffic is between 4- 5 pm (144 left turns) with at least 90 left turns recorded for all hours of the AM and PM peak traffic periods. b. For southbound CSAH 56, the cross product between southbound left turns and northbound opposing traffic peaks at around 9,800 in the AM peak period (6-7 am) and around 13,000 in the PM peak period (3-4 pm). The highest hour of southbound left turning traffic is between 7- 8 am (64 left turns). c. For eastbound Sunwood Drive, the cross product between eastbound left turns and westbound opposing traffic peaks at around 3,500 in the AM peak period (7-8 am) and around 11,500 in the PM peak period (4-5 pm). The highest hour of eastbound left turning traffic is between 5- 6 pm (56 left turns). d. For westbound Sunwood Drive, the cross product between westbound left turns and eastbound opposing traffic peaks at around 6,000 in the AM peak period (6-7 am) and at around 32,000 in the PM peal-, period (4-5 pm). The highest hour of westbound left turning traffic is between 4- 5 pm (146 left turns). Following up against the flashing yellow arrow criteria from the MnDOT Traffic Signal Timing and Coordination Manual: 1. There is sufficient turning room in the intersection so that left turn paths were not conflicting. 2. Only 1 left turn lane exists for each intersection approach, and there are less than 3 opposing through lanes of traffic facing each left turn lane. 3. The intersection is not anticipated to have an excessively high crash rate with respect to left turning movements.