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Transition from Crash Cushion to W-Beam Guardrail

State KY
Description Text

We are looking for details on guardrail transitions to crash cushions.  Specifically, the attached Quadguard detail shows thriebeam to guardrail.  Do you know if there is a MASH crash test on this configuration?  We may need to update our RBC-110 drawing which shows the connection details between a crash cushion and double-faced guardrail.








One more question: is double-faced guardrail MASH tested?  Or do we use regular guardrail testing to endorse the use of double-faced?










Thanks again for your assistance




W-beam Guardrails

End Treatment,Terminals and Anchorages

Date October 23, 2023
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Attachment RBC-110.pdf Attachment Quadguard W-Beam ( page 51).pdf

It is difficult for us to comment directly on specific crash cushion systems as they are proprietary technology. Because we did not design those systems or have access to design and testing data, we cannot make comments relative to their performance.


We can however make general comments on transitioning guardrail to various structures that may help guide you. The back end of crash cushion may be considered fixed objects and are similar to bridge rail AGTs. As such, we can evaluate them in somewhat similar ways.


The two transitions shown have different approaches. Your existing standard is a relatively short transition. Based on the work that we have done regarding AGT design, there may be concerns with the short upstream stiffness transition of this configuration


The Quadguard transition is functionally the thrie beam AGT that we have developed for the pooled fund adopted to a median installation and connected to the back of the crash cushion. This design likely has an improved chance to meet MASH TL-3 as it incorporates a similar stiffness transition and rail transition to our existing AGT configurations. A couple of additional items to note. This transition has not been tested in a median configuration. That evaluation is currently in the works in the Midwest Pooled Fund Program. The concern is mainly with small car impacts on the upstream end of the transition causing vehicle wedging and deceleration beneath the W-thrie transition section.  A second item to note is that we do not know the extent of potential vehicle snag on the downstream end of the transition as the vehicle reaches the rear of the crash cushion. That said, this is probably the best option without further R&D.


With respect to median guardrail, the MGS is MASH TL-3 compliant in a median configuration. Following the original MASH testing of the MGS, I submitted and received an eligibility letter request for the MGS median barrier to be considered MASH compliant based on the testing of the roadside system. Subsequent to that, TTI successfully tested the MGS median barrier to MASH TL-3.


Let me know if you have any questions.


Date October 24, 2023
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Attachment B-204 - MGS Median Barrier acceptance letter.pdf