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HomeMy WebLinkAbout155 - Vision Triangle Memo BOZEMAN, GREAT FALLS, KALISPELL & SHELBY, MT | SPOKANE, WA | LEWISTON, ID | WATFORD CITY, ND | MEDIA, PA 406.586.0277 tdhengineering.com 234 East Babcock Street Suite 3 Bozeman, MT 59715 MEMORANDUM Date: February 7, 2023 TDH Job No.: B22-007 To: Cody Flammond, PE - City of Bozeman Engineering Department From: Cody Croskey, PE Subject: 5th & Main Residences Vision Triangle Departure Supporting Information The purpose of this memo is to demonstrate how the proposed departure from the Street Vision Triangle standard for the 5th & Main Residences project can be accomplished without jeopardizing the public’s health, safety, and welfare while still meeting the intent of the standard. The proposed building will be located at the northeast corner of the intersection with storefront block frontages immediately adjacent to N. 5th Avenue and Main Street to satisfy the B-3 zoning district form & intensity standards which are in-line with the City’s growth policy. The corner of the building at the ground floor is planned to be pulled back outside of the street vision triangle in accordance with the standard. The upper floors, however, will overhang the street vision triangle and a single column must come down within the street vision triangle to support the upper floors in a structurally safe and reliable manner. The departure request is for the encroachment of this single column. A departure from the Street Vision Triangle standard was identified with the original site plan application materials for this project in accordance with BMC 38.400.100.E as the 5th and Main intersection is controlled by a traffic signal and Main Street is an MDT urban route. We also understand from previous correspondence during the Concept Review process that the City Engineering Department will likely support a departure from the Street Vision Triangle at this intersection for the following reasons: (i) The intersection is signalized. (ii) The sidewalk width is adequate to allow sighting of pedestrian traffic by motor vehicles. (iii) The encroachment and conditions at the intersection are consistent with other signalized intersections on Main Street. The following sight distance analysis is provided in accordance with MDT and AASHTO design standards to demonstrate how the proposed street vision triangle encroachment can exist without significantly impeding or obstructing the view of the traveling public at this intersection. t dhengineering.com PAGE NO. 2 FEBRUARY 7, 2023 Methods for determining Intersection Sight Distance (ISD) requirements at traffic-signal controlled intersections are provided in the Montana Traffic Engineering Manual developed by MDT, which uses gap acceptance design based on the criteria and theory presented in AASHTO’s A Policy on Geometric Design of Highways and Streets. Because this intersection is signalized in all directions, the controlling movement for sight distance at the northeast quadrant is a south-bound right turn from the minor road (N. 5th Avenue) onto Main Street heading west. The driver of the vehicle on the minor road must have sufficient clear sight distance of oncoming traffic to the right to make a safe departure in a right-on-red scenario. The attached exhibit shows the resulting intersection sight distance triangle required at this corner with a posted speed limit of 25 MPH following the Montana Traffic Engineering Manual Section 28.9.2. The proposed building and support column will not obstruct the required sight distance triangle, and the sidewalks are sufficiently wide to allow pedestrians to see and be seen before attempting a crossing using the existing pedestrian signals. Please let me know if you have any questions or require any additional information. Sincerely, Cody Croskey PE Civil Engineer TD&H ENGINEERING J:\2022\B22-007 Tracy Sub Block D\DOCUMENTS\REPORTS\Vision Triangle\5th & MAIN VISION TRIANGLE MEMO.DOC UPUPUPUPUPUPMAIN STREETN 5TH AVENUE ALLEY5TH & MAINRESIDENCESBUILDINGDESIGNED BY:QUALITY CHECK:JOB NO.FIELDBOOKDRAWN BY:DATE:B22-007 EX-1 SIGHT DISTANCEREV DATE NOT FORCONSTRUCTION REVISION 5TH & MAIN RESIDENCES BOZEMAN, MONTANA INTERSECTION SIGHT DISTANCE EXHIBIT B22-0072.7.23.DWGSHEETEX-1CJCEngineering 234 E. BABCOCK ST., SUITE 3 • BOZEMAN, MONTANA 59715 406.586.0277 • tdhengineering.com