Board of Adjustment Agenda and Packet 2011 06 15

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ENGINEERING CONSULTANTS "Your Project, Our Pride" conflicting vehicles. AASHTO standards are widely accepted and are commonplace criteria to follow in roadway design. We feel that following AASHTO criteria in no way disregards the City of Louisville safety concerns with respect to providing drivers an adequate field of vision at intersections, merely refines the potential impacts the current code has on areas adjacent to intersections. J3 has analyzed the AASHTO method of calculating sight triangle geometry and applied the results to the intersection of Kaylix Avenue and Paschal Drive to provide an example of the potential reduction that could be yielded verses the City's current method. The results are provided in the attached exhibit, along with the supporting calculations. The difference in the geometric layout of sight/vision triangles between the Louisville Code and AASHTO method can be summarized by the fact that AASHTO accounts for physical vehicle location in relation to the intersection, the speed of oncoming traffic (design speed), approach grades and the distance the stopped vehicle must cross through the intersection in order to get to their designated travel lane (or time gap). The City of Louisville code applies a standard distance along the property lines of the intersection to set the triangle, which overestimates the required sight triangle requirements resulting in generally over -encumbering the corner lots with non -buildable area. It should be noted that J3 calculated the sight triangles are based upon the assumption that Louisville will be installing stop signs at the Minor Street for the intersections. We formally request your review of the presented information and if you find it acceptable, are requesting that Steel Ranch (Takoda Subdivision) receive a waiver from current measurement location in the Municipal Code for applying Vision Clearance Areas at intersections along right-of- way. In lieu of the current City of Louisville Code methodology, we suggest utilizing a similar requirement of 30' measurement applied at the flowline intersection point for street to street connections with a reduced requirement for alleys. Our suggestion is not groundbreaking and is consistent with many municipalities along the Front Range. We have provided excerpt from a local municipal code at the end of this letter as demonstration of the potential modification. The suggestion is to generate a Vision Clearance Area that fully protects the AASHTO Intersection Sight Distance requirements without adversely impacting the surround areas. As an option, case by case evaluation of the individual intersections to the AASHTO criteria could be utilized in lieu of the triangle methodology. We appreciate your consideration of this request and are available to discuss this request further. Respectfully Submitted, 13 Engineering Consultants, Inc. Bryan Clerico, P.E. cc: file 3151 South Vaughn Way, Suite 680 • Aurora, Colorado 80014 Phone: 303.368.5601 • Fax: 303.368.5603 • J3Engineering.net