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I have a project where project staff may have to flare beam guard at a greater rate than what is listed in table 5.7 of the RDG.  What research was used to develop this table?   Does MwRSF have any guidance on this topic?

Just yesterday, I was asked about flare rates for concrete barrier.  Does MwRSF have some research on this topic?

I am attaching a pdf copy of a MwRSF research report regarding flare rates. As noted in the MwRSF Report No. 157, the guardrail flare rates were determined by James Hatton, FHWA. Unfortunately, I do not believe that these flare rates were based on actual full-scale vehicle crash testing.

Later, MwRSF conducted a flare rate study involving the MGS which shown that flare rates as steep as 5:1 were acceptable. I have provided a link to download this report if you cannot find it. Of course, our guidance in this report pertains only to the MGS.

The file 'TRP-03-191-08.pdf' (86.7 MB) is available for download at

for the next 7 days.

It will be removed after Wednesday, May 26, 2010.

Finally, I have included a pdf copy of a journal paper covering the flare rate topic that may also provide more refined conclusions and guidance. In Section 8 of the paper and based on computer simulations, the authors note that the modified G41s may not perform effectively when installed with flare rates steeper than 15:1 under TL-3 impacts under NCHRP Report 350.

Years ago and while at TTI, Dean prepared guidelines for temporary concrete barrier. I believe those guidelines are published in NCHRP Report 358.

It should be noted that the reserach performed on maximum flare rates for the MGS were based on NCHRP Report No. 350 impact conditions. These flare rates have not been evaluated with MASH TL-3 impact conditions. Further study is necessary to evaluate the maximum allowable flare rate for MASH impact conditions. Additionally, research is currently underway to identify crashworthy configurations of approach guardrail transisions with a flared installation; several full-scale crash tests of flared transitions have been unsuccessful when evaluated to MASH TL-3 impact conditions. A crashworthy configuration has not yet been identified.