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I’ve got an interesting situation at a railroad underpass (old bridge and narrow shoulders – see attached).  Currently, thrie-beam mounted at 32” and quarter post spacing is in place (installed somewhere around 2002).  It’s being removed as part of an overlay project to bring the barrier up to standard.  My first thought was concrete barrier rail, but given the cost, that probably won’t fly with the District.  So I’ve been considering another thrie-beam installation.  Looking at TTI’s Report 614341-01, I see a 34” thrie-beam system passed MASH. But given the working width of 5.5 feet and ZOI considerations, I’m concerned it may not be what we want here.

So, here’s my question – is there another option I can look into that I’m missing?

Thanks much.

There are a couple of other options here for reduced deflection guardrail. TTI has tested the MGS with reduced post spacing to MASH TL-3. Additionally, they also worked on NCHRP 22-38, which looked at further guardrail deflection reduction options. I believe there are transition options for both systems.

I have attached both reports. Let me know if you have any questions.

https://www.roadsidepooledfund.org/wp-content/uploads/2023/06/TRNo610211-01-Final-REV-1-Signed.pdf

https://nap.nationalacademies.org/catalog/27772/mash-tl-3-deflection-reduction-for-31-inch-guardrail-a-guide

Thanks!