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We have been reviewing Valtir’s new end terminal, the 4F-T, and I’d be interested in your thoughts. I wonder if other DOTs have reached out to you about this end terminal? This terminal seems like a hybrid between flared and parallel and it appears like it would require custom guardrail design for this terminal.

I asked Valtir the following question (their response in blue):

• All the testing and images I have seen has parallel W-beam leading up to this end terminal. Is there any concern with a flared W-beam?
  
  
  
  • Although it was not tested in this configuration, a 25:1 flare of the LON single ply 12ga W-beam guardrail (w- 6’ 3” post spacing for a minimum of 12’-3”) prior to the 4F-T™ should not be of a concern based on the testing information presented by MwRSF at the 2025 ATSSA Expo, as well as what we observed during testing.  
  
  
  • It is important to note that the 4F-T™ itself IS to installed with the 8.6:1 flare relative (parallel) to the roadway. (4’ straight flare over 34’ 4-1/2” in length)
  
  
  
  

We use AASHTO guidance for flaring guardrail (Table 5-9 in the Roadside Design Guide) which allows for much higher flares than 25:1. Currently the only flared end terminal KDOT has on their PQL is the MFLEAT. KDOT would like to have another flared terminal on our PQL for competition/bidding but I don’t think this terminal fits our current standard drawings and would require a special design.

I would welcome your thoughts or conversations you have had with others about this terminal.

Thank you,

The issue of flare rate for W-beam is tricky right now.

1. We previously evaluated flare rates for the MGS under NCHRP Report 350 impact conditions. In that study, we were able to achieve a maximum flare rate of 5:1. Because of the increased rail section and strength of thrie beam, we would be reasonable to assume that thrie beam could achieve similar flare rates under NCHRP Report 350 systems.
   1. https://mwrsf.unl.edu/researchhub/files/Report92/TRP-03-191-08.pdf
2. MASH evaluation of flare rates has been underway at TTI for several years. TTI has evaluated flare rates of 11:1, 21:1, and 25:1 with the MGS. All of these tests have failed due to rail rupture or anchorage failure. As such, a MASH compliant flare rate for W-beam guardrail has yet to be established at this time.
3. The RSI MFLEAT flared terminal has been tested along it redirective length under MASH TL-3 conditions with a flare rate of 13.3 :1, and the 4F-T terminal was tested at an even higher flare. This testing was at the beginning of LON of the terminal and was relatively close to the end anchorage. Both the 4F-T and the MFLEAT use a little over 4’ post spacing. This would suggest that other flare rates are achievable, but the TTI testing noted above has not proven that out.
4. We also have evaluated flared thrie beam AGTs. The testing we have done on flared AGT systems failed with flares of 15:1 and 20:1. These failures were due in part to gouging of the wheel into the thrie beam corrugations. A 25:1 flared AGT system did meet MASH TL-3.

Thus, while some terminals and AGTs have successfully been tested with flares under MASH, we have not seen similar outcomes for W-beam in the testing at TTI and would have some concerns with flared W-beam until the issues observed at TTI are resolved.

Let me know if you have further questions or want to discuss further.

Thanks!