A while back MnDOT had a conference call with you guys to discuss various issues related to barriers. One particular issue we discussed was the slope of the top of a tall (TL-5) concrete F barrier at a guardrail connection. Based on the discussions, MnDOT decided that for such barriers taller than 34”, we would use a barrier top slope no steeper than 1:8 at barrier terminations and guard rail connections. We have since begun the process of updating our standards to reflect this change, but this has led to another question…
In the attached drawing (pages 1 & 2), we show 2 barrier top slope options in the red boxed area (one dashed line, one solid line). The dashed line indicates the slope of the barrier if we match the geometry from our typical barrier end sections for barriers less than or equal to 34 inches in height (the typical barrier end condition is shown on the 3rd page, in red boxed area), the second option shown on pages 1 & 2 is a solid line with a 1:8 slope that terminates at a height of 2’-5” above the roadway surface. Any opinion on which of these 2 options is preferred for a TL-5 barrier?
I’ll also be contacting you again in the near future to set up a conference call to discuss options for developing a new single slope barrier standard for MnDOT. It’s likely we’ll propose a slope that doesn’t match that of states like Wisconsin, Texas, and California. I’ll send out more info regarding this issue next week.
From the attached details, I would say that I prefer the solid gray line versus the dashed gray line. It is flatter for passenger vehicles and less likely to allow the engine hood/front quarter panel to excessively gouge/grind on the upper surface. We will be available for the future discussions as well.
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