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X City of Arden Hills Page 8 of 63 October 7, 2022 The MnDOT Bicycle Facility Design Manual states that on the roadway side, the preferred minimum separation (termed “buffer”) between a sidepath and edge of roadway or face of curb roadway is six feet, with two feet as an absolute minimum in constrained areas. Depending on expected sidepath use and traffic volumes/speeds on the adjacent roadway, a wider buffer and narrower sidepath may be preferred. Also, buffer widths of three feet or less should be paved as grass or other vegetation may struggle to thrive. On the outside of the sidepath, the minimum separation (termed “clearance”) between the edge of a sidepath and the edge of the right-of-way is two feet, however if users are unlikely to shy away from the adjacent land use, designers may consider reducing the clearance distance to one foot. If these buffer/clearance widths are not maintained, the operating width of the sidepath is effectively reduced on the side(s) where the buffer/clearance is not provided. Refer to Figure 2 in Appendix A, which has been updated accordingly. The MnDOT Bicycle Facility Design Manual states that if the adjacent outside slope is sloping away at flatter than 1V:3H with a dropoff height at the bottom of the slope of six feet or less, a two foot width adjacent to the path graded at 1V:6H is needed, and if the adjacent outside slope is sloping away at 1V:3H or steeper with a dropoff height at the bottom of the slope of six feet or less, a five foot width adjacent to the path graded at 1V:6H is needed. If the dropoff height at the bottom of an outside slope at 1V:3H or steeper is six feet or more, a fence or safety rail is needed along the top of the slope. Different combinations of slopes and dropoff heights require different heights of fence. In cut conditions where the adjacent outside slope is sloping upward away from the path, no side slope protection is needed. Refer to Figure 2 in Appendix A, which has been updated accordingly. Although the cost difference between bituminous and concrete fluctuates over time, generally concrete remains at a higher cost than bituminous, and in that case it does not improve or enhance the project sufficiently to warrant the option, therefore a concrete pavement alternative was not included in this updated report. Also, a bituminous pavement was recommended based on geotechnical information (see Section 8.0 Geotechnical Evaluation). Further, all four of the previously-constructed portions of the proposed trail have been constructed with bituminous, so there would be a consistency benefit to using bituminous for the portions of the trail remaining to be constructed. However, it is still recommended that in the final design phase of the project, the cost difference between bituminous and concrete be revisited to confirm that using concrete remains cost-prohibitive. In the portion of the proposed trail remaining to be constructed, the only portion that may warrant a concrete barrier to provide additional protection from adjacent high speed traffic is the portion along US Highway 10 if the proposed trail were constructed along the east side of the corridor. This updated report recommends that the proposed trail be located on the west side of the corridor (refer to Section 4.0 Design Approach), therefore no barriers need be considered if this recommendation is followed. The MnDOT Bicycle Facility Design Manual uses the term “buffer” for the distance between the trail and the adjacent roadway and explains that many factors influence the buffer width, including type of roadway, posted speed, traffic volumes, the presence of paved shoulders, bike lanes, and parking lanes, and the potential use for signs, utilities, storm water infiltration, shade trees, roadside vegetation, and snow storage. As noted above, the preferred sidepath buffer width is six feet and minimum sidepath buffer width is two feet. There are not specific buffer width criteria for different types of roadways and posted speeds, instead designers are encouraged to follow these few criteria and the other guidance to determine the appropriate buffer width. Refer to Figure 2 in Appendix A.