Existing geometric design guides provide deterministic design criteria for highway
\nelements which ignore the uncertainty associated with many design inputs and model
\nparameters. Reliability analysis has been advocated as an approach to account for this
\nuncertainty and to evaluate the risk associated with a particular design feature. This paper
\ndiscusses one important application of reliability analysis: the calibration of geometric design
\nmodels to yield consistent safety (risk) levels. In order to illustrate the concept, the paper
\nconsidered the case of restricted sight distance on horizontal curves due to existence of median
\nbarriers. The paper provides calibrated design charts for the middle ordinate (M), defined as the
\nlateral distance between the edge of median barriers and the centerline of the inside traffic lane,
\nat different probability of non-compliance levels. The impact of several factors on the calibrated
\ndesign charts are discussed including the use of operating and design speeds and the target
\nprobability of non-compliance.
\nThe results show that the calibrated values of the middle ordinate (M) are generally lower than
\nthose derived from the AASHTO design guide. The AASHTO design guide is so conservative
\nespecially at high speeds and sharp curves. The results elucidate that significant reductions to
\ncurrent design requirements could be obtained at reasonable reliability (risk) levels. The
\ncalibrated design charts can offer designers dealing with highways with constricted right-of-way
\nan option to use lower middle ordinate values and enable them to estimate the safety
\nconsequences of their decisions. Overall, the calibrated charts can aid the decision maker in
\ndetermining the safety implications of deviating from geometric design standards and
\nquantifying the safety level built in design values that are deemed acceptable.<\/p>\n
<\/div>","protected":false},"excerpt":{"rendered":"
Mohamed Hussein, Tarek Sayed, Karim Ismail, Adinda Van Espen<\/p>\n","protected":false},"author":163,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_kad_post_transparent":"default","_kad_post_title":"default","_kad_post_layout":"default","_kad_post_sidebar_id":"","_kad_post_content_style":"default","_kad_post_vertical_padding":"default","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_kad_post_classname":"","footnotes":""},"categories":[128,346],"tags":[],"class_list":["post-18737","post","type-post","status-publish","format-standard","hentry","category-2014-cmrsc-ccmsr-xxiv-vancouver","category-research-and-evaluation"],"acf":[],"_links":{"self":[{"href":"https:\/\/carsp.ca\/en\/wp-json\/wp\/v2\/posts\/18737","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/carsp.ca\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/carsp.ca\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/carsp.ca\/en\/wp-json\/wp\/v2\/users\/163"}],"replies":[{"embeddable":true,"href":"https:\/\/carsp.ca\/en\/wp-json\/wp\/v2\/comments?post=18737"}],"version-history":[{"count":1,"href":"https:\/\/carsp.ca\/en\/wp-json\/wp\/v2\/posts\/18737\/revisions"}],"predecessor-version":[{"id":18826,"href":"https:\/\/carsp.ca\/en\/wp-json\/wp\/v2\/posts\/18737\/revisions\/18826"}],"wp:attachment":[{"href":"https:\/\/carsp.ca\/en\/wp-json\/wp\/v2\/media?parent=18737"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/carsp.ca\/en\/wp-json\/wp\/v2\/categories?post=18737"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/carsp.ca\/en\/wp-json\/wp\/v2\/tags?post=18737"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}