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The basic ZOI guidance from our original study is organized nicely in section 5.5.2 of the RDG. The original report is attached as well.

Note that this guidance is certainly not all encompassing and does not detail all of the variations in your table.

The guidance we developed previous has NCHRP 350 recommendations for TL-4 barriers as shown below. In the original study, we did not differentiate between barrier shapes and had a range of heights. We have not had the opportunity to revisit those numbers. As such, that is likely our best conservative guidance for TL-4 under NCHRP 350 for vertical, single-slope, and safety shape barriers.

This data does include a range of NCHRP 350 TL-4 barrier heights. We only had one data point for a 42” tall TL-4 barrier. This was the BR27C bridge rail, essentially a vertical shape. This had a ZOI of 24”. Values for single slope and safety shapes were not available. Base on this, we have previously noted the potential to estimate the ZOI for TL-4 single-unit truck impacts to be 24 and 12 in. for 42 and 54-in. parapets, respectively. Please note that this information is very only an estimate due to the unavailability of crash test data corresponding to your noted conditions.

Those numbers will likely change under MASH TL-4, but that research has not been undertaken. As such, we have no MASH TL-4 data or guidance. We were recently awarded NCHRP 22-34 to determine MASH ZOI values, so we should be developing revised guidance in the future.

In terms of TL-5 ZOI numbers, we have looked into this previously for a few states. The following were the ZOI measurements from a 42” tall TL-5 bridge rail and a 42” tall TL-5 median barrier tests conducted at MwRSF between 2004 and 2007.  The critical ZOI value was found to be 76.5" - measured from the median barrier crash test.

Bridge Rail - Working width = 79.5"

                     Top corner offset from front of barrier = 5.5"

                     ZOI = 74"

Median Barrier - Working Width = 86.5"

                     Top corner offset = 2" (lower slope)+ 8" (head offset) = 10"

                     ZOI = 76.5"

The ZOI values were calculated from the working widths (measured from high speed video) and the offset distance between the top-front corner of the barrier and the front of the barrier.  Both of these barriers incorporated a head slap prevention geometry, so the top of the barrier was offset above 35" in height.  If you wanted to apply these ZOI numbers to a vertical parapet, conservatively you could add back in the offset distances noted above for a ZOI of 86.5”. Note that these values are the upper values only. We have not calculated the lower values. We should calculate those as part of NCHRP 22-34.

For TL-5 safety shape parapets, the best current guidance would likely be to use the values for the median barrier noted above. Impacts on safety shape parapets may change the ZOI somewhat, but the effect is unknown.

For 54” tall TL-5 barriers, we only have data from the Manitoba bridge rail work that we did recently. That barrier was a near vertical single slope with a height of 49.25”. Based on the working width of that system, which was 37.4” as measured from the bottom of the face of the barrier, the ZOI would be 31.65” as measured from the top front corner (barrier had a top corner offset of 5.75”). Note that this number would be conservative for a 54” tall TL-5 barrier. Similar recommendations to those made for the 42” tall TL-5 vertical and safety shape barriers would apply here as well.

Let me know if that helps and if you have further questions.

Thanks