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I need to start this response by clarifying that evaluation of this transition placed on slopes has never been performed (testing or numerical analysis). The report you referred to on retrofitting transitions (TRP-03-266-12) was focused on two different transitions utilized by the the state of Wisconsin. Additionally, that project only focused on the downstream end of the transition. Evaluation of the w-to-thrie beam stiffness transition has never been performed on sloped terrain. Thus, a crashworthy transition system has never been developed for use on or adjacent to fill slopes. In order to ensure system crashworthiness, you would need to provide 2-ft of level grading behind the transition posts. Of course, it would be costly and labor intensive to add the required soil to the roadside. If you chose to install a transition without the required grading, the recommendations below are our best guess at what it would take to make the transition perform as intended. Please do not take these recommendations as a standard for new construction.  Rather, these should only be utilized to improve existing systems without the possibility of significant grading work to the site.

 Report TRP-03-266-12 provided guidance pertaining to additional posts to be driven behind existing 7-ft transition posts. These replacement posts were conservatively designed assuming the original posts would provide no additional resistance compared to the new post. Thus, the same "additional" posts would be recommended as replacement posts. As described in the report, the size and embedment depth of the replacement posts depends on the slope of the roadside. Steeper slopes will require larger posts. So, an 8.5-ft long W6x12 post was recommended for 3:1 slopes, while a 12-ft long W6x16 was recommended for 2:1 slopes. Please use this report to guide your selection of post for use as Post nos. 1-6 depending on the terrain slope on site.