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Attachment 2. Memo from Toole - Lane width standards and approach for Bluff Creek Boulevard dated June 13, 2017TooleDes gnGroup IIL 212 Third Aveiue Norti+, Suac 476 Mit ,apo[Ls, MN 55401 612.534.4094 .- .uoedesian.com MEMORANDUM Date: 6/13/17 To: Kendra Lindahl, AICP Organization: Landform From: Christopher Bower, P.E. Project: Avienda Re: Lane Width Standards and Approach for Bluff Creek Boulevard Existing Conditions The proposed roadway is an extension of Bluff Creek Boulevard, which was previously constructed with 16' lane widths, as shown below. The existing 16' roadway width provides enough space for an emergency vehicle to pass a stopped car in the unlikely event that a vehicle impedes emergency access. Design Intent The goal of our design for Bluff Creek Boulevard is to create a roadway corridor that accommodates a range of motorized and non -motorized users, and encourages users to walk and bike between destinations within and beyond the proposed development. Our roadway design helps achieve this goal through the use of landscaping, medians, frequent pedestrian crossings and the overall minimization of the roadway cross section. This creates a more comfortable and safe environment for all users — something that can be experienced on existing Bluff Creek Boulevard, especially when compared with larger, less comfortable roadways such as Lyman or Powers Boulevard, whose wide roadway sections and lack of landscaping lead to higher vehicle speeds and longer (and less comfortable) pedestrian crossings. Design Standards Bluff Creek Boulevard will be designed in accordance with MnDOT's State Aid Standards (Minn. Rules Chapter 8820), along with applicable AASHTO and MnDOT design guidelines. The proposed Bluff Creek Boulevard will be a Collector or Local roadway with ADT < 15,000. Per Minn. Rules 8820.9936, applicable standards and proposed dimensions are shown below: Design Criteria Minimum Standard Proposed Bluff Creek Design Design Speed 30-40 mph 30 mph Lane Width 11,feet (wherever possible, lane widths of 12 feet, rather than 11 feet, should be used) 12 feet Median Curb Reaction Distance 1 foot 2 feet Minimum Median Width 4 feet 7 feet Outside Curb Reaction Distance 2 feet 2 feet Clear Zone (area adjacent to roadway that is clear of fixed objects, such as trees) 1.5 feet (when posted speed is 40-45 mph) At least 5 feet The proposed roadway meets or exceeds all applicable State Aid design standards, and as designed should be wholly adequate for the intended use. Impact of Lane Widths on User Safety MnDOT's current technical memorandum on lane widths (No. 13 -18 -TS -07), includes a discussion on the role of lane widths in both pedestrian and motor vehicle crashes. An excerpt from this technical memorandum is included below, with certain sections underlined for emphasis. Urban and Suburban Highways and Streets Special care is demanded for design in urban and suburban environments, where often limited space must be balanced between the various transportation modes and among geometric design elements. Lane width is particularly important on multi -lane streets, where even small variations in design values are multiplied across the cross section. One research study has found that narrower lanes on urban and suburban streets were generally associated with lower crash frequencies compared to wider lanes. (An exception to this is four -lane undivided streets, where 9- and 10 -foot lanes have been associated with higher crash frequencies than wider lanes respectively.) Furthermore, narrower cross sections reduce crossing distances and have been associated with reduced travel speeds, both direct factors in the safety of pedestrians. For these reasons, lane widths on urban and suburban streets should be designed no wider than to adequately accommodate the vehicular traffic volume and composition. General design guidance is as follows: Lane widths of 11 feet are a good fit for a wide variety of urban arterials and collectors. 11 -foot lanes are fully adequate for vehicular operation on low -speed facilities and can be thought of as roughly equivalent in terms of comfort and usability to 12 -foot lanes on high-speed roads and streets. 11 -foot lanes are also appropriate on high-speed facilities under favorable geometric conditions. Lane widths of 10 feet are typically most suitable where truck and bus volumes are relatively low and design speeds are 35 mph or less, as well as in more constrained circumstances. Lane widths of 12 feet tend to be most applicable in high-speed or high -demand circumstances. On low -speed facilities, the use of 12 -foot lanes should be limited to very high demand conditions or to limited -access roadways, so as to avoid wherever practical the drawbacks often associated with overly wide cross sections, such as excessive speed and longer pedestrian exposure. Multimodal considerations Mobility and safety apply to all modes of travel in the right of way. The ability of non -motorized users to travel along and across streets and highways safely and comfortably is a principal measure of livability. As discussed earlier in this section, the lane width selection for urban and suburban streets will often significantly affect vehicular operating speeds and the distances pedestrians face in crossing roadways. Bicycles and pedestrians are among the most vulnerable roadway users, and vehicular speed and exposure are the two primary factors in non -motorized users' crash frequency and severity. Conclusion The most current research and policy has found that overly wide roadway sections can result in higher vehicle speeds, longer pedestrian crossings, and ultimately results in an increase in both crash frequency and severity. The proposed roadway section is already wider than recommended in current MnDOT guidance in the interest of corridor consistency and conformance with State Aid design standards. Any further increase in the roadway width cannot be supported by existing best practices or guidance, and should be expected to lead to a reduction in overall user safety. Ensuring timely and effective emergency response is of paramount importance, along with promoting roadway user safety. We hope to arrive at a roadway design that accomplishes both goals, and we believe that maintaining the existing 16' wide roadway section is the appropriate response.