Federal Highway Administration
1200 New Jersey Ave. S.E.
Washington, D.C. 20590
December 6, 2007
Mr. Reinhardt F. Cyphers
Addresses of Distinction, LLC
907 New Franklin Road
LaGrange, GA 30240
Dear Mr. Cyphers:
In your mail correspondence of October 18, 2007, you requested the Federal Highway Administration’s (FHWA) acceptance of your company's aluminum tubes as a breakaway sign support. You referenced our acceptance letter SS-28 which reported on small sign support testing conducted in “weak” soil by the Florida Department of Transportation (DOT). In that letter we accepted as breakaway 3 inch (89 mm) diameter, 6061-T6 alloy aluminum tubes of 0.187 inches (4.75 mm) thickness when no more than one sign support was used within a seven foot span. The posts pulled out of the ground partially or completely, allowing the vehicle to gradually come to a stop. The two sign supports that you request to use have: (1) a diameter of 2.875 inches (73 mm) with a wall thickness of 0.203 inches (5.16 mm) and (2) a diameter of 2.375 inches (60 mm) with a wall thickness of 0.154 inches (60 mm). The three sign posts are compared in the following table:
|Sign Post||Florida DOT||Addresses of Distinction, LLC||Addresses of Distinction, LLC|
|Diameter||3.5 in (89 mm)||2.875 inches (73 mm)||2.375 inches (60 mm)|
|Wall Thickness||0.187 in (4.75 mm)||.203 inches (5.16 mm)||0.154 inches (60 mm)|
|Tensile Strength||45 ksi (310 MPa)||30 ksi (207 MPa)||27ksi (186MPa)|
|Yield Strength||40 ksi (275 MPa)||25 ksi (173 MPa)||21ksi (145Pa)|
|Cross Sectional Area||1.951 in2 (1257 mm2)||1.70 in2 (1099mm2)||1.70 in2 (1099 mm2)|
In addition to the Florida DOT sponsored testing to which you referred, earlier tests of 4 inch (100 mm) diameter thin-walled aluminum tubes were conducted in “strong” soil. These posts, which were fitted with anti-rotation hardware below the ground, fractured upon impact and were found to be crashworthy.
Your company’s aluminum tube sign supports are smaller diameter and made of weaker alloy than the posts already found to be crashworthy in either strong or weak soil. Therefore your request regarding the two aluminum tube sizes to be used as sign supports as stated above is acceptable for use on Federal-aid highway projects when requested by a State.
Please note the following standard provisions that apply to FHWA letters of acceptance:
George E. Rice, Jr.
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