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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 3^rd
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.