10-02-2017 Council Packet - Laserfiche WebLink

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MnMUTCD: 2B.13 Speed Limit Sign A Standard: Speed zones (other than statutory speed limits) shall only be established on the basis of an engineering study that has been performed in accordance with traffic engineering practices. The engineering study shall include an analysis of the current speed distribution of free- flowing vehicles. The speed limit (R2-1) sign shall display the limit established by law, ordinance, regulation, or as adopted by the authorized agency based on the engineering study. The speed limits displayed shall be in multiples of 5 mph. Speed Limit signs, indicating speed limits for which posting is required by law, shall be located at the points of change from one speed limit to another. An Option: Other factors that may be considered when establishing speed limits are the following: • Road characteristics, shoulder condition, grade, alignment, and sight distance • The pace speed • Roadside development (nearby school) and environment • Parking practices and pedestrian activity (mainly children) • Reported crash experience for at least a 12-month period Methods and Practices for Setting Speed Limits: An Informational Report by the FHWA Safety Program: Most engineering approaches to speed limit setting are based on the 85th percentile speed—the speed at which 85 percent of free-flowing traffic is traveling at or below. The typical procedure is to set the speed limit at or near the 85th percentile speed of free-flow traffic. Adjustments to either increase or decrease the speed limits may be made depending on infrastructure and traffic conditions. The 85th percentile speed method is also attractive because it reflects the collective judgment of the vast majority of drivers as to a reasonable speed for given traffic and roadway conditions. This is aligned with the general policy sentiment that laws (i.e., speed limits) should not make people acting reasonably into law-breakers. Setting a speed limit even 5 mph below the 85th percentile speed can make almost half the drivers illegal; setting a speed limit 5 mph above the 85th percentile speed will likely make few additional drivers legal. Under the operating speed method of setting speed limits, the first approximation of the speed limit is to set the speed limit at the 85th percentile speed. The MnMUTCD recommends that the speed limit be within 5 mph of the 85th percentile speed of free- flowing traffic. The posted speed limit shall be in multiples of 5 mph.