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We are considering using the 31" Midwest guardrail system.  We have been using the test data and drawings to develop our own standards, but I have a few outstanding questions about the applicability  of this guardrail.  

How much shoulder is needed behind the 6' post to provide sufficient support?  I trying to get a handle on appropriate uses for the 6' post vs. the 9' post.  

Has there been any testing of type 12 anchors for the 31" guardrail?

Has there been any testing of double faced guardrail for median applications?

How much shoulder is needed behind the 6' post to provide sufficient support? I trying to get a handle on appropriate uses for the 6' post vs. the 9' post.

For MGS guardrail:

1. Standard MGS guardrail placed adjacent to any slope with 2' of level soil behind the posts is acceptable.

2. For MGS guardrail placed 1'-2' adjacent to a 6:1 or flatter slope, standard 6' W6x9 posts at standard spacing are recommended.

3. For MGS guardrail placed 1'-2' adjacent to a 3:1 to 6:1 slope, 7' W6x9 posts at standard spacing are recommended.

4. For MGS guardrail placed less than 1' adjacent to a 3:1 or steeper slope, 9' W6x9 posts at standard spacing are recommended.

Has there been any testing of type 12 anchors for the 31" guardrail?

I am not sure what the type 12 anchor is without more details. I have attached the anchorage that we tested with and that we recommend for non-terminal locations.

Has there been any testing of double faced guardrail for median applications?

We have an FHWA approved median barrier version of the MGS. See the attached details.