Agenda - Public Works Committee - 03/15/2022

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Mr. Bruce Westby, PE February 28, 2022 Page 5 Any changes to the operation of the left turn signal phases are not anticipated to impact overall operations of the intersection in a negative way (and delays for left turning traffic will decrease with flashing yellow arrow operations which will improve the overall operation of the intersection). The following modifications to the existing signal system installation will be required to revise the operation of this signal system and add flashing yellow arrows for all intersection approaches: For northbound and southbound CSAH 56, the overhead end mounted and far left pole mounted left turn signals for these intersection approaches will require having 3-section RLA-YLA-GLA signal heads replaced with 4-section RLA-YLA-FYLA-GLA signal heads. No additional cabling will be required to be installed to operate these signal heads based on a review of the field wiring diagram, as there are sufficient spare conductors available to allow for the new 4-section signal heads to be installed. No additional through traffic signal heads will be required to be installed for these approaches, as each approaching through lane has its own separate signal centered on the lane. For eastbound Sunwood Drive, either a 5-foot extension or installation of a 5 foot longer mast arm to replace the existing 35 foot long mast arm will be required to be installed in order to be able to center a new left turn signal head over the approaching left turn lane. For the purposes of the estimated construction costs included in this analysis, replacement of this mast arm was included in the Engineers estimate of construction costs, as is typical policy for signal systems on Anoka County roadways and operated by the County. The overhead and far left pole mounted 5-section signal heads would then be replaced with new 4-section RLA-YLA-FYLA-GLA signal heads. A new 3-section RYG signal head with either a strap - on mid mast arm mount (on the existing mast arm) or a new mid -mount (on a new mast arm) will be required to be furnished and installed so that a RYG signal head is able to be centered on the approaching through lane. No additional cabling will be required to be installed to operate these signal heads based on a review of the field wiring diagram, as there are sufficient spare conductors available to allow for the new 3-section and 4-section signal heads to be installed. For westbound Sunwood Drive, either a 5-foot extension or installation of a 5 foot longer mast arm to replace the existing 35 foot long mast arm will be required to be installed in order to be able to center a new left turn signal head over the approaching left turn lane. For the purposes of the estimated construction costs included in this analysis, replacement of this mast arm was included in the Engineers estimate of construction costs, as is typical policy for signal systems on Anoka County roadways and operated by the County. The overhead and far left pole mounted 5-section signal heads would then be replaced with new 4-section RLA-YLA-FYLA-GLA signal heads. A new 3-section RYG signal head with either a strap - on mid mast arm mount (on the existing mast arm) or a new mid -mount (on a new mast arm) will be required to be furnished and installed so that a RYG signal head is able to be centered on the approaching through lane. No additional cabling will be required to be installed to operate these signal heads based on a review of the field wiring diagram, as there are sufficient spare conductors available to allow for the new 3-section and 4-section signal heads to be installed • With regards to left turn lane detection, the MnDOT Traffie Control Signal Design Manual recominends that either four loop detectors be installed for proper detection (at 5', 20', 35' and 50' from the stop bar or crosswalk) or that two separately wired loop detectors be installed for existing signal system retrofits at 10' and 40' from the stop bar or crosswalk. Recent County practice has been to have the four separate loop detectors installed in each left turn lane in order to be able to operate the left turn lanes on non -lock operation. For this signal system, four (4) left turn lane detectors were previously installed at 15 foot spacing and in close proximity to the stop bar on both Sunwood Drive intersection approaches (with separate lead-in cables for 2 of the 4 loop detectors in each left turn lane). Thus, no loop detector work is required to be completed for the Sunwood Drive approaches. For the CSAH 56 approaches, left turn lane detection was installed at 10' and 40' from the stop bar for these intersection approaches (each wired separately). To meet current County practice, additional loop detectors will be required to be furnished and installed -5 feet and 25 feet from the stop bar in both left turn lanes.