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There is very little testing of low height barriers to MASH TL-2. However, we have been looking into it as part of an existing combination bicycle railing project with Iowa.

In that study we reviewed, previous crash testing of low profile barriers. We found that a parapet height between 24 in. (610 mm) and 32 in. (813 mm) could possibly provide adequate results during testing. However, due to the increased C.G. height and vehicle mass of the 2270p versus the 2000p vehicle, which alters the vehicle’s performance, further analysis was needed to select an appropriate barrier height that will be able to contain the vehicle.

We conducted LS-DYNA simulation modeling of low height vertical parapets with the 2270P vehicle. It was determined that the Silverado model could not accurately model vehicle override. The inability of the vehicle model to predict override the barrier was attributed to the tire model as well has the suspension. The suspension used on the truck model does not and could never completely imitate the suspension of the actual vehicle causing the vehicle behavior to not be completely accurate. The tires used in this model also do not exactly match the behavior of tires in the real world. The combination of these two things prevented the vehicle model from overriding the barrier.

In order to further evaluate potential TL-3 barrier heights, we compared the height of critical 2270P vehicle components with previous TL-2, low-height barrier tested with the 2000P vehicle. An example is shown below.  

You can see that he main vehicle capture components that were used in the capture of the 2000P vehicle on a low-height (22”) tall parapet would still be effective for the 2270P vehicle impact. However, some of the 2270P components are higher relative to the barrier as compared to the 2000P vehicle and the 2270P vehicle has more mass.

Based on this we recommended to Iowa that we were confident that a 24” tall parapet would meet MASH TL-2. We also noted that 27” would be a more conservative option, but we did not think it was necessary. Of course this has not been tested. Iowa has agreed to go with the 24” parapet with a bike rail mounted on top, but plans to use the 24” parapet without the rail as well.

We are working on the setup for testing this system to TL-2 this summer and should have a good idea about how it redirects the 2270P when that is done.

We also developed details for the TL-2 parapet. I have attached them for you to see. Please don’t distribute these as the research is not finalized and Iowa has yet to ok them for testing.

Let me know if that helps or if you need anything else.

Thanks