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I have reviewed the report for NCHRP Project No. 20-07 Task 395 to determine if this railing, or something similar to it, has been evaluated against the MASH 2016 safety performance guidelines and estimated design impact loading. Within the report, two bridge railings seem to be somewhat similar: (1) aesthetic parapet tube B-25-J railing from Michigan [pages 102-105 and 180-187] and (2) S-352 series steel tubing concrete combination railing from Vermont [pages 107-109 and 198-208].

From a quick review, it is evident that the two railings in the NCHRP report have an additional, lower railing that has been added between the upper rail and the parapet. Both systems use six No. 4 longitudinal bars with 60 ksi steel. The Grade 60 vertical steel consists of No. 4 bars at 8 in. centers for both systems. The posts and upper rail have similar sizes. Your detail does not depict a lower steel tube rail.

TTI researchers have rated the two systems as expected to meet MASH Test Level 4. At this time, I do not have access to the research that led to the addition of a second steel rail, which was likely added to mitigate vehicle snag on posts with passenger vehicles. I will inquire to my colleagues to see if they know any additional history.