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I believe you guys tested long span guardrail with long-post but I am having issues finding the report.  Attached is the location of the project with details and our standard drawing for long span.  The issue seems to the 8:1 grading behind the post that we require.  Brock would like to use the long span over the culvert but use the long-post guardrail detail where the slope break point is at the face of the rail.  Has this been tested and passed the testing?

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For some background, this is a culvert replacement project. The existing 64”x43” CMP Arch is on a 70 deg. L.F. skew, making it a bridge. The goal was to try to reduce the skew with a replacement culvert enough to relegate it back to a culvert from a bridge. I am proposing a 60” Reinforced Concrete Circular pipe at a 60 deg. L.F. skew, which can accomplish this goal by being just under a 10’ span and meet the necessary hydraulics.

There is a slew of obstacles on this project including a gabion wall that we can’t disturb on the inlet side as well as topography that includes 2:1, or greater, backslopes on both sides of the road. These obstacles have greatly limited my options in regards to re-grading the ditches and streams to match the new culvert alignment.

Due to the limited room to work, I have to reduce the graded shoulder and use long posts per note P of L&D V.1 301-3 for the couple of additional feet that can provide. And, due to the skew of the culvert, I can’t simply omit a guardrail post over the culvert and call it a day because the posts won’t clear the OD of the pipe.

When looking at SCD MGS-2.3, I see that long-span requires 2’ of 8:1 grading behind the posts, as well as 25’ of this 8:1 grading that extends at least 25’ beyond the limits of the long post section. And in the notes of MGS-2.3, the Materials reads “for other details not shown, see SCD MGS-1.1”. Based on that reference to MGS-1.1, is it possible to spec long span (18.75’) with long posts as detailed in MGS-1.1 and reduce the 2’ of 8:1? I can’t seem to find anywhere that specifies whether this is a viable or crashworthy option.

For reference: on the left, my typical section currently has a 6’ graded shoulder with 4’ being treated and a 4’ offset of guardrail from the traveled way; on the right, my typical section has 4’ of treated/graded shoulder with guardrail 4’ from the traveled way.

Revising my typical to include the additional grading may not be completely impossible on the left side, but it will definitely be challenging based on chasing the aforementioned foreslopes; on the right, there is the existing gabion wall downstation and a ~1.5:1 foreslope upstation that begins ~6’ from the EOP and there is no way around either one.

There are MASH TL-3 developed and tested options for guardrail on slope that can be used on 2:1 slope like you have shown below.

There have also been long span guardrail systems tested to MASH TL-3. However, the long span systems have only been evaluated with 2’ of level terrain behind the posts. We have a project that just started to evaluate the long span system at the slope break point of a 2:1 slope with longer posts. However, that research just started this month and the post configuration has not been established. We also need to run crash tests to evaluate the system.

So unfortunately there is no crash tested configuration for your situation, but we do have research in the works.

Let me know if you need anything else.