MASH compliance of transition for W-beam guardrail to single slope permanent barrier

#10183 October 10, 2023 Ariel Sheil ( [email protected]) Texas A&M Transportation Institute


Shawn Debenham

[email protected]


MASH compliance of transition for W-beam guardrail to single slope permanent barrier

TTI Project 616391 designed and tested a transition from W-beam guardrail to anchored F-shape portable concrete barrier. Can the results of this crash testing be used to assume MASH compliance of the attached transition design for connecting the W-beam guardrail to a permanent single slope barrier?

Attached Files

  1. Nauman Sheikh ( [email protected]) Texas A&M Transportation Institute

    Hi Shawn,

    After reviewing TTI crash test report 616391-01 of the W-beam guardrail transition to anchored F-shape PCB, and noting the design similarities with the attached proposed transition details, I am of the opinion that the attached transition design can be considered MASH TL-3 compliant. This conclusion is based on the following observations:

    – The guardrail to barrier attachment details of the attached design closely match those of the TTI crash tests 616391-01-1 & 2.

    – Even though the TTI tests involved an anchored F-shape PCB, the deflection of the PCB was very small during the tests (2.75 inches max. permanent deflection in Test 3-11). Due to the small deflection of the barrier, it can be concluded that it behaved as nearly rigid/permanent barrier. This would be similar to the performance of the proposed permanent concrete barrier in the attached transition detail.

    – TTI tests were performed with the F-shape profile PCB, whereas the attached details are for a single slope profile barrier. The single slope barrier profile is generally considered to result is slightly more stable redirection of an impacting vehicle compared to the F-shape profile. More importantly, however, the barrier profile in this transition design is covered by thrie-beam guardrail, which is further offset from the traffic face of the concrete barrier and spaced with wood blocks. This reduces the influence of the barrier profile. Furthermore, the bottom toe of the F-shape profile extends towards the traffic side more than the bottom of the single slope profile. Considering these factors, the change in the barrier profile from F-shape to single slope is expected to result in similar or slightly better performance.

    – The F-shape barrier in the TTI transition tests was 32 inches tall. The single slope barrier in the attached transition detail transitions from 32-inch height at the guardrail end to 42-inch height over 7 feet. This results in a vertical slope of 6.8 degrees. Past testing of similar systems, for example TTI Test 605641-1, has successfully passed MASH Test 3-11 with an upward slope of 11.8 degrees, which leads to the conclusion that the height transition of the single slope barrier in the attached transition detail is not expected to result in negative consequences in MASH testing.

    Based on the above observations, it is my opinion that the attached transition detail can be considered MASH TL-3 compliant. If you have any questions, please let me know.

    Best regards,

Leave a Reply

Your email address will not be published. Required fields are marked *