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Newmont I County Road 82 Guardrail Analysis <br /> J Analysis <br /> 3 Analysis <br /> 3.1 Eastbound Traffic <br /> With a 35 MPH design speed the required clear zone is 12' based on an assumed increased <br /> traffic volume on the low end of the range between 750-1500 ADT (see Appendix A). The <br /> current roadway eastbound section includes a 12' lane with approximately a 7' shoulder. <br /> Parallel to the shoulder is an existing ditch varying widths and depths. The ditch fore slope <br /> varies from 4:1 to 1.5:1 sides slopes are defined as horizontal run:vertical rise therefore a 4:1 <br /> slope is 4' horizontally to 1 foot vertically. Anything steeper then 4:1 slope is considered a non- <br /> recoverable slope and anything steeper than 3:1 is considered traversable, but not recoverable. <br /> In essence any slopes steeper than 4:1, within the clear zone, guardrail protection should be <br /> considered. Since some portions of the existing ditch fore slopes and back slopes are greater <br /> then 4:1 and are within the required clear zone, they create a potential hazard for any traffic that <br /> veer outside of the shoulder. These slopes should be flattened to meet clear zone requirements. <br /> The existing slopes beyond the clear zone are generally graded out at a 4:1, considered <br /> recoverable, to the WHEX highwall or the existing trail depending on location. This 4:1 slope, a <br /> minimum 150' in length, is beyond the required clear zone. (See Appendix B for a typical cross <br /> section). <br /> 3.2 Westbound Traffic <br /> With a 35 MPH design speed the required clear zone is 17' based on an assumed traffic volume <br /> on the low end of the range between 750-1500 ADT and a horizontal correction factor of 1.4. <br /> The horizontal correction factor is a conservative value based on the 500' horizontal curve near <br /> the overlook parking area. Current road conditions provide a clear zone of 19', when the <br /> Eastbound Traffic lane (12') and the average existing shoulder(approximately 7') are added <br /> together. This distance exceeds the clear zone requirement for the Westbound Traffic. <br /> 4 Conclusion <br /> Based on both its current distance and general side slopes beyond the clear zone required for <br /> CR82 the WHEX highwall meets the requirements for a clear roadside. Shielding of the highwall <br /> with guardrail may be considered as a viable safety option it must also be considered that a <br /> guardrail in of itself is a roadside hazard and use of guardrail must be evaluated carefully. Given <br /> the existing roadside side slopes are generally 4:1 beyond the clear zone for CR82 it is our <br /> opinion that the eastbound traffic does not require guardrail, although slope modifications in the <br /> existing roadside ditch should be considered in order to meet clear zone requirements <br /> recommended by AASHTO's Roadside Design Guide 4th Edition design criteria. Those <br /> modifications include re-grading the existing ditch fore slopes to maintain a minimum 4:1 slope <br /> inside the clear zone. It is not required, but our opinion that the ditch back slope be re-graded to <br /> meet the 4:1 slope as well to provide additional recoverable slope for traffic that could veer <br /> outside of the travel way. <br /> hdrinc.com 2060 Briargate Parkway,Suite 120,Colorado Springs,CO 80920-1045 <br /> (719)272-8800 <br /> 3 <br />