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What Resources are Available? The newly revised statute requires that the safety, engineering, and traffic analysis done when considering a speed limit change must consider national urban speed limit guidance and studies. Therefore, it is important to understand the difference between national guidance, research, and advocacy documents. National Guidance The Federal "Manual on Uniform Traffic Control Devices" (MUTCD) is the national standard for all traffic control devices installed on any street, highway, bikeway, or road open to public use. It also provides guidance on establishing speed limits. Minnesota agencies are statutorily bound to comply with MUTCD guidance. The "Minnesota Manual on Uniform Traffic Control Devices" (MN MUTCD) was developed to establish standards and to provide a uniform policy for the use of traffic control devices in the State of Minnesota. The MN MUTCD correlates with and conforms closely to the current system as approved by the American Association of State Highway Officials (AASHTO) and the national Manual on Uniform Traffic Control Devices (MUTCD). Other Studies and Research Guidance for the Setting of Speed Limits (NCHRP 17-76)' This study created two tools (one with macros and one without) that could better inform speed limits beyond the 85th percentile. These tools take factors such as urban vs rural, other roadway users, and roadway type into account. Design Speed, Operating Speed and Posted Speed Practices, (NCHRP Report 504)' This report summarized previous research and data collected through mail surveys. The findings were that there needs to be guidance added for the relationship between the 85th percentile and the posted speed limit. Speed limits are generally set 4-6 mph less than the 85th percentile speed. This report also added the need to specify radius, grade, access density, median presence, on -street parking, pedestrian activity, and signal density when determining speed. Effects of Raising and Lowering Speed Limits on Selected Roadway Sections (FHWA)' Although the changes in vehicle speeds were small, driver violations of the speed limits increased when the posted speed limits were lowered. Conversely, violations decreased with the speed limits were raised. This does not reflect a change in driver behavior, but rather, a change in how compliance is measured. No evidence to support crash experience changing with speed limit changes. Speed Concepts: Informational Guide (FHWA) 4 Study found as speed increases, crash severity increases. There is not proper guidance on speed limit through the design phase. The 85th percentile may be higher than anticipated, especially on low or moderate speed roads. The design speed is NOT the maximum safe speed. Reducing the speeds without other changes is likely to result in a small reduction of operating speed. Posted speed limits should always be within 5 mph of the 85th percentile speed. 1 Guidance fort he Setting of Speed Limits, NCHRP, 2019 2 Design Speed, Operating Speed, and Posted Speed Practices, NCHRP, 2003 a 3 Effects of Raising and Lowering Speed Limits on Selected Roadway Sections, FHWA,1997 4 Speed Concepts: Informational Guide, FHWA, 2009 Page 140 of 185