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I've got a couple of questions for you:

1.         Could you send me a picture or description of the current guidance for ZOI for a 42" F-shape concrete barrier at TL-3, TL-4, and TL-5 conditions (if available)?

2.         Are you aware of any minimum and/or maximum allowable height guidance for thrie-beam guardrail?

3.         Has an equivalent wood post design been determined for use with the MGS at the breakpoint of a 2:1 slope?

1.         Could you send me a picture or description of the current guidance for ZOI for a 42" F-shape concrete barrier at TL-3, TL-4, and TL-5 conditions (if available)?

** I will do some digging on this one. I may need to review the past 26 consulting summaries to find the answer.

2.         Are you aware of any minimum and/or maximum allowable height guidance for thrie-beam guardrail?

** I am not aware of the performance limits for this barrier in terms of maximum and minimum height. However, I will seek comment from my colleagues and review a prior TTI report to see if testing at variables heights was included.

3.         Has an equivalent wood post design been determined for use with the MGS at the breakpoint of a 2:1 slope?

** Yes, the wood post equivalent is a 6-in. x 8-in. by 7.5-ft long SYP post. A draft research report has been initiated but remains incomplete at this time.

You may be a little surprised that the wood post equivalent to a 9-foot long W6x9 is a whole 1.5 feet shorter. However, the 9-ft and 8-ft W6x9 post lengths were fairly close when we selected the 9-ft length. I also believe post-soil forces are higher now than before " due to MASH installation procedures that were finalized in the latter years of the MASH document and performance specification for soil. Thus, the 7.5-ft wood post length is not that far off of the original two options. We re-conducted some steel post tests on a 2:1 slope so that we would have a comparison of the two material types with newer MASH installation procedures and soil conditions. Those comparisons are contained in the draft report.

In 2022, the results of NCHRP Project 22-34 were published. In this report, ZOIs were recorded at MASH TL-2, TL-3, TL-4, and TL-5 impact conditions for various barrier heights; the ZOIs were not strongly linked to the profile or shape of the barrier impacted. Recommended ZOIs for 42-in. tall barriers for MASH TL-3, TL-4, and TL-5 impact conditions are shon in the attached.

The results of NCHRP Project 22-34 were published in NCHRP Report No. 1018, located here: https://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=4379

https://www.trb.org/Publications/Blurbs/182863.aspx