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FHWA web site

http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/ctrmeasures/wbeam/

First Sentence:

               
Recent research on standard 27-inch strong steel-post W-beam guardrail shows
that it does not meet NCHRP Report 350 Test Level 3 criteria.

Do you know what are they referring to?

There were a number of historical crash tests that demonstrated problems with many versions of 27” tall W-beam guardrail. In addition, some variations even had problems at a 27¾” height. This discussion has been ongoing for the last 8 or more years. Over the last 3 or 4 years, FHWA has been discussing and presenting options for raising guardrail height. I believe that they raised this issue at our Pooled Fund meeting, the joint meeting between the Pooled Fund and AASHTO TF13, and several AASHTO TF13 meetings. We had a NCHRP 22-14 crash test on the G41s that showed it marginally met AASHTO MASH at 27¾” height under Test Level 3.

FHWA prepared and released a lengthy memo on this topic many years ago. I can send a copy of this memo after locating if desired. Also, I can send a copy of a 2007 TRB paper that we prepared after doing the AASHTO MASH update study.