Federal Highway Administration
400 Seventh St., S.W.
August 30, 2007
In Reply Refer To: HSSD/CC-94A
Mr. Steve L. Brown
Trinity Highway Safety Products Division
P.O. Box 568887
Dallas, Texas 75356-8887
Dear Mr. Brown:
In the Federal Highway Administration’s (FHWA) acceptance letter CC-94 dated September 2, 2005, we accepted a modified version of your ET-Plus guardrail terminal named the ET-Plus 31. On January 16, 2007, you requested that the FHWA extend our acceptance of the ET-Plus 31 to include 6 inch x 8 inch wood posts. On April 24, 2007, you followed up with additional information that we requested.
The modifications noted below were needed to match the ET-Plus terminal, which was originally tested with standard W-beam guardrail, to the Midwest Guardrail System (MGS). The MGS barrier was formally accepted as an National Cooperative Highway Research Program (NCHRP) Report 350 test level 3 (TL-3) barrier on March 1, 2005, (acceptance letter B-133). To verify the crashworthiness of the modified ET-Plus, the Texas Transportation Institute (TTI) conducted the following two tests, which are described in that agency's July 2005 report, "NCHRP Report 350 Testing of the ET-Plus for 30-inch High W-Beam Guardrail":
To match the MGS barrier design, the following modifications (shown in CC-94) were made to the original ET-Plus terminal:
Your present request is to allow either the SYTP or 6 inch x 8 inch wood posts in the ET-Plus 31 as shown in the enclosed drawing. Because the 6x8 wood posts have been shown to perform in a similar manner to steel posts (including the SYTP) the wood post ET-Plus 31 may be considered a TL-3 design that can be used on the National Highway System when connected to the MGS barrier. While the barrier itself is non-proprietary, your terminal is proprietary and remains subject to the conditions stated in Title 23, Code of Federal Regulations, Section 635.411 when used on Federal-aid highway projects. All other conditions in the FHWA acceptance letter CC-94 continue to apply.
George E. Rice, Jr.
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