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The layout that you are proposing looks reasonable in terms of installation lengths and transitioning from AGT to ½-post MGS to ¼-post MGS to ½-post MGS to standard post spacing MGS (or terminal).  I just have a couple of comments about ¼ post spacing MGS:

1. Reduced spacing MGS systems (either ½-post or ¼-post spacings) have not yet been evaluated to MASH, so we can’t say with any certainty that these configurations are MASH crashworthy.  Generally, we feel that these reduced post spacing MGS configurations will perform adequately.  However, we do have some concerns with these systems when impacted by the small car as it may lead to excessive snag and/or rail tearing.  Note, the 350 evaluation of the ¼-post spacing system did not include a small car – we have sense come to realize the critical nature of small car impacts on special applications of W-beam guardrail.  TTI’s pooled fund just recently voted to evaluate reduced post spacing MGS as part of their research program, so we should know the results from this evaluation in the next couple of years.
2. From the picture you included, the pole looks very close to the guardrail system.  Under NCHRP 350 impact conditions, the dynamic deflection of the ¼-post spacing MGS was measured at 18”, and the working width of the system was 36”.  These values are likely going to increase under MASH conditions.  Thus, if the pole is closer than 36” from the face of the W-beam, or 17” from the back of the posts, the pole is susceptible to being impacted during redirections (it would be inside the working width of the system).  You may not have a lot of other options, but wanted to at least make you aware of this issue.

Let me know if you have further questions.

One other question.  What are your thoughts about attaching the MGS transition to the pier?  See the picture below.  We thought that the MGS transition would be a stiffer transition than our current GP Transition (see below).  We are also not sure where the GP transition was developed.  I know you like to attach the MGS transition to the standard buttress, so if you saw any problem with the MGS transition attaching to the pier we would just go with our current GP transition that has in-service performance history.  Thank you for your thoughts.  I will try not to follow with another question after this one, we are just wanting to keep good notes on our special case areas.  Thanks again.

Attaching any guardrail transition to a tall vertical wall/pier is not recommended.  Impacting vehicles can, and will, roll towards the barrier and extend over the top of the guardrail during redirection.  Thus, the vehicle will contact and snag on the tall concrete structure.  Obviously, not good for safety performance.  

All successfully developed and tested transition buttresses incorporate vertical slopes on the upstream end of any barrier taller than 32” to prevent such snagging from occurring.  As a point of reference, the standardized buttress has a height of 32” at its upstream face and utilizes a 6:1 vertical slope to increase its height and match up with the height of the adjacent bridge rail (36”, 42” 54”, ect…).   Other buttress designs have utilized similar vertical slopes.  Now, in the case of a very tall structure , like a pier, you wouldn’t need to provide a height transition all the way to the top of the pier – a vehicle would never extend over a barrier that tall.  We have seen vehicle hoods extend over 42” tall barriers, so the transition may need to extend up to around 50” in height to prevent vehicles from extending over and snagging on the pier.

Also, the guardrail in the picture seems to be very low (probably from roadway overlays), but you probably already new that was an issue.  I just have to say something when I see issues J

Let me know if you have questions about anything above.