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Technical Memorandum To: Jason Wedel, PE Copy: City of Lino Lakes From: Chuck Rickart, PE, PTOE Date: January 7, 2014 File: WSB No. 2029-59 Subject: Speed Concern Evaluation Process - Tart Lake Road The purpose of this memorandum is to provide a process to evaluate requests related to speed concerns on City roadways. The primary goal is to have set guidelines and procedures in place to address these concerns. Following the outline of the process is an evaluation of a speed concern on Tart Lake Road between Otter Lake Road (CR 84) and 24th Avenue/Elmcrest Avenue. ROADWAY ELIGIBILITY In order for a roadway to be eligible for speed mitigation/traffic calming, it needs to meet the following criteria. • Classified as a local or collector street • Length greater than 1,000 feet • Traffic volumes greater than 1,500 vehicles per day • Posted speed of 30 mph or less • Cannot be a cul-de-sac EVALUATION PROCESS If the roadway is eligible for speed mitigation/traffic calming, a preliminary study will be conducted using data collected by a speed awareness display (SAD) or road tubes. In analyzing the speed data, the 85th percentile speed of the collected data will be calculated. The 85th percentile speed is defined as the speed at or below which 85 percent of the traffic is moving.1 1 Federal and State speed limit guidelines define the 85th percentile speed as a “reasonable speed” or the speed in which 85% of motorists travel at or below. Experience has shown that the 85th Percentile Speed most closely provides for a safe and reasonable speed limit. Therefore, it can be expected that on a typical roadway, approximately 15 to 20 percent of the vehicles may be traveling at speeds greater than the posted speed limit. St. Cloud  Minneapolis  St. Paul Equal Opportunity Employer wsbeng.com