Max Post Height of Buried-in-Backslope Terminal

#9857 May 30, 2023 Roadside Pooled Fund ( [email protected]) Colorado

We recently received a question that revolved around if there is a max post height for a Buried-in-Backslope terminal. In looking into it, it appears that the previous NCHRP-350 version used to call out a max height of 45″ (1125 mm). See page 7 of the attached TTI Report and page 5 of the attached FHWA Eligibility letter. The most recent MASH test report (see attached Test Report #608431-01-1&2) does not state a max height. We think a reasonable max height would be 49″ (31″ rail height + 18″ under rail at ditch line), but we are wondering if TTI could provide an engineering opinion on this with any thoughts.

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  1. Roger Bligh ( )

    The maximum rail height in the MASH testing of the buried-in-backslope terminal, which dictates the maximum post height, was 49 inches (31-inch rail height + 18-inch ditch depth). This is considered an acceptable tested height.
    Other terrain variations are being investigated under a Roadside Safety Pooled Fund Project entitled “Buried-in-Backslope Terminal Variations in Foreslope, Backslope, and Ditch Configurations.” Additional guidance related to maximum acceptable rail/post height may result from this project.

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