June 16, 2004
Refer to: HSA-10/CC-12M
Hayes E. Ross, Jr., P.E., Ph. D.
Professor Emeritus and Research Engineer
Texas Transportation Institute
College Station, Texas 77843-3135
Dear Dr. Ross:
In your May 25, 2004, letter, you requested approval from the Federal Highway Administration to allow use of your Cable Release Post (CRP) or your Hinged Breakaway Post (HBA) as the first post in a Test Level 2 (TL-2) ET or ET-Plus guardrail terminal, followed by three posts that can be either timber CRT posts, weakened wood posts in steel tubes (both with and without soil plates, depending on tube length), HBA posts, or 6x8.5/6x9 SYTP posts.
Based on previous crash tests and earlier acceptances of various post combinations, the design alternatives listed above may be considered acceptable for use with the previously accepted ET/ET-Plus TL-2 design, provided posts 2, 3, and 4 are all the same type of breakaway post. As noted in acceptance letter CC-12H, dated February 18, 2000, users should be advised that the TL-2 design is considered crashworthy only for speeds up to 70 km/h (43.5 mph) and is therefore not recommended for use at locations where higher impact speeds are probable.
(Original Signed By R. Powers)
John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety
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