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Do you know what the lowest installation height for wbeam guardrail (G41S)would be for a TL-2 application?

The reason I asked that we may be able to use this as guidance for leave in place guardrail for routine maintenance.  I recall that Dean was doing research on approipriate test levels for roadways that was based on a B/C type analysis.  In other words a TL-2 device could be 

justified on a 55+ mph roadway in lieu of TL-3.   Does this sound 

familiar to you and is that done?

The tolerance for routine maintenance is still needed.  Requiring DOTs to upgrade all guardrail that is less then 27.75" except on 3R/4R or new construction is not practical.  As you already know there are many 

other improvements that would have much better B/C ratio.   Such as 

horizontal curves, sight distance, and access control projects to name a few.

We have investigated the guardrail height issue. The findings indicate that 27" should be able to work at TL-2 impact conditions. We even went as far as investigating 25" and the results were inconclusive if it had a chance of working at TL-2 impact conditions.

In addition, as written in the pre-proposal for the TL-2 MGS Bridge Rail that Kansas submitted during the past pooled fund meeting, previous testing of standard W-beam guardrail and the MGS with rail height of 27" and 27-3/4" indicate that a 27" tall MGS Bridge Rail is plausible if limited to TL-2 applications.