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Mr. Bruce Westby, PE <br />March 21, 2017 <br />Page 4 <br />movement, where protected left turn phasing was run together for these movements <br />with no conflicts between either direction's left turn movements. Left turn <br />movements are offset far enough such that no conflicts in left turn paths are <br />occurring. <br />2. As mentioned, the westbound approach has two left turn lanes. For this approach, the <br />MnDOT Manual suggests that protected operation be utilized during the higher <br />volume periods of the day with Engineering judgment being used to determine if <br />flashing yellow operation could be used for all other times of the day. <br />3. There are less than 3 opposing lanes of through traffic facing each intersection <br />approach. <br />4. The intersection does not have a high crash rate and there is no significant history of <br />right angle crashes involving left turning traffic. <br />In summary, as there is no significant crash history for left turning traffic and traffic volumes are <br />likely lower for the entire intersection (outside of the peak traffic periods), the City should be <br />able to consider using Flashing Yellow Arrow operations at this intersection throughout much of <br />a typical weekday and throughout the weekend. In addition, any changes to the operation of the <br />left turn signal phases are not anticipated to impact overall operations of the intersection in a <br />negative way (and delays for left turning traffic will decrease with flashing yellow arrow <br />operations which will improve the overall operation of the intersection). For peak traffic periods <br />though (and for when sun becomes an issue for eastbound and westbound traffic), protected left <br />turn operation is strongly recommended to be implemented. <br />Some modifications to the existing signal system installation will be required to revise the <br />operation of this signal system and add flashing yellow arrows for each intersection approach. <br />Both overhead end mounted and far left pole mounted left turn signals for each intersection <br />approach will required having 3-section RLA-YLA-GLA signal heads replaced with 4-section <br />RLA-YLA-FYLA-GLA signal heads. For the westbound approach (due to the dual left turn <br />lane), a 5-foot extension will be required to be added to the mast arm facing this approach so that <br />two 4-section overhead signals can be installed and centered on each left turn lane (requirement <br />that each approaching left turn lane have its own flashing yellow arrow signal centered on each <br />left turn lane). No additional through signal heads will be required to be installed facing any of <br />the four approaches, as there are already separate through (RYG) signal heads centered on each <br />through lane. Some additional cabling (6/c#14) will be required to be installed to operate new <br />flashing yellow arrow signal heads on all four intersection approaches based on a review of the <br />field wiring diagram. No new conduit will be required to be installed to accommodate <br />installation of these new cables. <br />With regards to left turn lane detection, the MnDOT Traffic Control Signal Design Manual <br />recommends that either four loop detectors be installed for proper detection (at 5', 20' 35' and <br />50' from the stop bar or crosswalk) or that two separately wired loop detectors be installed for <br />