We did look at MGS placement at large offsets behind curbs under both MASH TL-2 and TL-3 impact conditions.
https://mwrsf.unl.edu/researchhub/files/Report72/TRP-03-205-09.pdf
https://mwrsf.unl.edu/researchhub/files/Report56/TRP-03-221-09.pdf
https://mwrsf.unl.edu/researchhub/files/Report47/TRP-03-237-10.pdf
As part of that analysis we provided guidance on envelopes for placement of the MGS at large offsets behind curbs depending whether or not the barrier was installed at 31” with respect to the roadway, or with respect to the top of the curb (37” tall with respect to the roadway. We then tested the MGS installed at 31” with respect to the top of the curb at an 8’ offset to evaluate the boundary of that guidance. This test failed.
Subsequent to that analysis, we performed a simulation analysis to evaluate similar offsets under MASH TL-2 conditions. From that analysis, we determined that a 6 ft offset was critical. We full-scale crash tested the 6 ft offset and got acceptable performance under TL-2. We noted at the time that no relevant TL-2 crash tests were available for 1100C and/or 2270P vehicles striking a curb without other barriers located behind the curb. Thus, a maximum 12-ft lateral offset is recommended; since, prior TL-3 curb testing indicated potential vehicle problems beyond a 12-ft lateral offset. Computer simulation had indicated that a 4’ minimum offset was acceptable for TL-2.
The study described above was not truly sufficient in terms of funding and scope to fully investigate the variations in lateral offset and barrier heights for the MGS with curb and further study is definitely needed. These ranges could be fully developed and validated. Currently, we don’t have enough data to determine the performance outside of the conservative ranges chosen in the above study.
In terms of using large curb offsets with AGTs, that effort has never been undertaken to the best of my knowledge. Thus, the best current guidance would likely be to use similar offsets to what we have recommended for the MGS.
We have answered related questions in the past. See below.
https://mwrsf-qa.unl.edu/view.php?id=1074
thanks
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