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For a single slope concrete median barrier (TL-3 to TL-5), keeping a range of heights of crashworthy barriers, some are shown below, I am wondering what is the maximum slope face recommended to avoid vehicle/truck barrier climb or instability issues?

                                                                                         Test Level       Height (in)     Base Width (in)     Top Width (in)      Slope Face (degree)

CALTRANS Type 60 single-slope                                 3                 36                                                                                                             9.1

Ohio unreinforced single-slope                                  3                  42                          28                              12                                         10.8

TxDOT Median barrier                                                      4                  42                          24                                8                                          10.7

Thanks,

To date, single slope barriers have not been tested with slopes shallower than 11 degrees. Steeper slopes, including vertical faces, have been successfully evaluated. The concern with shallower slopes is that the face of the barrier can promote increased vehicle climb and instability. The point at which the slope angle increase becomes an issue is not fully defined. As such, I cannot say definitively whether or not the slope tolerances pose an issue or not. One would think that minor variations from the 10.8 degree nominal slope would not be sufficient to induce vehicle instability, but the point at which the shallower slope becomes a stability problem has not been fully defined.