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Mr. Bruce Westby, PE <br />March 21, 2017 <br />Page 5 <br />existing signal system retrofits at 10' and 40' from the stop bar or crosswalk. Recent County <br />practice has been to have the four separate loop detectors installed in each left turn lane in order <br />to be able to operate the left turn lanes on non -lock operation. For this signal system, left turn <br />lane detection was installed at 10' and 40' from the stop bar for the northbound, southbound, and <br />westbound approaches (each wired separately), while the eastbound approach has four loop <br />detectors installed in the left turn lane. To meet current County practice, additional loop <br />detectors will be required to be furnished and installed 25 feet and 55 feet from the stop bar in <br />the northbound and southbound left turn lanes as well as in both westbound left turn lanes (for a <br />total of 8 new loop detectors). No additional 2/c#14 cables or controller cabinet loop detector <br />cards will be required to operate these new loop detectors since existing loop detectors are <br />already wired separately in each left turn lane. <br />To allow for flashing yellow arrow operation, we estimate that these modifications (completed <br />by an electrical signal contractor) will cost approximately $40,000. A detailed preliminary <br />engineer's estimate of costs is attached to this letter for your information. <br />Overall, we do not see any issues with installation and operation of flashing yellow arrows for <br />each intersection approach. However, should the City and County implement flashing yellow <br />arrow modifications to this signal system, we recommend that the signal system initially <br />operate with protected left turns during both the AM peak period (6:00-9:00 am) and the <br />PM peak period (3:00-7:00 pm) due to higher traffic volumes, higher posted speeds, and <br />the presence of dual left turn lanes through this area. For all other hours of the day and for <br />all weekend hours, the City and County should be able to consider using flashing yellow arrow <br />operations. <br />Note that any changes in the operation of this signal system should be monitored by the City and <br />County, including annual review of crash data to ensure that crash frequency does not increase <br />due to modified left turn signal operations. <br />Please review our analysis and feel free to contact me at 651.490.2073 with any questions or <br />concerns that you may have related to our analysis. <br />We hope that this information provides you with insight needed to help evaluate and implement <br />the appropriate left turn operations for this intersection. <br />Sincerely, <br />SHORT ELLIOTT HENDRICKSON INC. <br />olm M. Gray, PE <br />Project Engineer <br />Enclosures <br />c: Jane Rose, Anoka County Highway Department <br />