View Q&A

In 2001, MwRSF conducted a series of NCHRP Report No. 350 full-scale vehicle crash tests on a metric-height, W-beam guardrail system attached to a concrete box culvert. The configuration include a half-post spacing for post anchored to the top of the box culvert and five half-post spacing beyond the culvert. One successful crash test was performed with the back of the post positioned 18 in. away from the culvert headwall. However, a second crash test was unsuccessful when the post was positioned 1 in. away from the culvert headwall. These results are summarized in MwRSF report no. TRP-03-114-02 as well as TRR No. 1853 (2003).

In late 2002, MwRSF submitted a request for FHWA acceptance with the posts positioned a minimum of 10 in. away from the culvert headwall based on extensive film analysis. Subsequent correspondence with FHWA ensued in 2003.

At the time, Dick Powers was reviewing and preparing FHWA acceptance letters. From the correspondence between FHWA and MwRSF, it became apparent that a couple of issues may create concern with the approval. First, FHWA desired that a more intense approach guardrail transition be included beyond that shown in the report even though the post behavior for the attached posts and embedded posts were nearly identical. The recommended transition included farther reduced post spacing and guardrail nesting; since, another Texas W-beam transition was used to attach to a very stiff Texas W-beam bridge railing. Second, there was a potential issue with the allowable lateral offset to the headwall. Based on a verbal discussion of these issues over the phone, we decided to pull the request for acceptance as we did not agree to the caviats that would be placed in the FHWA letter. Therefore, no final FHWA acceptance letter was published, even though preliminary discussions occurred while reviewing a draft letter. Some of the email correspondence has been obtained from the hard copy archives for this project.

Therefore, I would like to know what you would like to come out of this investigation and determine if some type of resubmission is desired for the metric-height guardrail system. It may be necessary for both MwRSF and KsDOT to have a phone conversation with FHWA to discuss our options as well. It may be the case that FHWA will no longer provide 350 approval letters for previously crash-tested systems. I look forward to hearing from you on this matter.

Per your request in a recent phone conversation, MwRSF will investigate and re-evaluate our prior request to seek acceptance of the system noted above as well as a similar system with the MGS. Thus far, I have found a copy of the original letter request, as contained in the attached pdf copy. However, I have not found the prior email correspondence on this matter between Dick Powers, FHWA, and MwRSF. I will look into our hard paper archives on this matter or contact FHWA to see if they have archived files regarding this request. I would think that we would need to start with original testing before moving on to MGS.