February 22, 1999
Refer to: HMHS/SS-68D
Mr. Lawrence Leahy
President, Xcessories Squared
P.O. Box 135
Auburn, IL 62615
Dear Mr. Leahy:
This is in response to your letters of January 13 and June 15, 1998, to Mr. Nicholas Artimovich of my staff requesting Federal Highway Administration acceptance of a variation in your company's triangular multidirectional slip base. You provided additional information of September 10, 1998, in response to our request.
We have previously found your "SB8" breakaway slip bases acceptable for single post supports on September 18, 1996, (Geometrical and Roadside Design Acceptance Letter SS-68) and for dual and triple post supports on December 29, 1996, (SS-68A). These designs used triangular plates measuring 8 inches (203 mm) on a side.
Your current request is for an identical breakaway design using "10 inch" (254 mm) triangular slip plates. This larger base (the "SB10") would accommodate a 3-inch (76.2 mm) square tube sign support. You indicated that the largest sign you would recommend for use on a single post with the SB10 base is 3.25 square meters (35 square feet). However, you do not recommend the SB10 slip base with 76.2 mm square (3 inch square) steel post be used with a winged anchor in soil when carrying more than 1.86 square meters (20 square feet) per each support. You recommend a heavy wall anchor set in concrete be used as a foundation for this application.
Due to the acceptable performance of the "SB8" system when tested with a single post, we believe that the subject slip base will perform in an acceptable manner. Therefore, single 3-inch square supports using the "SB10" slip base are acceptable for use on the National Highway System within the range of conditions tested and with the limitations you have placed on it, when requested by a State. This acceptance letter, numbered SS-68D, shall not be reproduced except in full.
Our acceptance is limited to the breakaway characteristics of the supports and does not cover their structural features. Presumably, you will supply potential users with sufficient information on structural design and installation requirements to ensure proper performance. We anticipate that the States will require certification from Xcessories Squared that the slip base hardware and posts furnished will have essentially the same chemistry, mechanical properties and geometry (except as modified for the larger size) as that used in the tests, and that they will meet the FHWA change in velocity requirements.
The SB10 Slip Base is a "proprietary" product. To be used in Federal-aid projects, except exempt, non-NHS projects: (a) must be supplied through completive bidding with equally suitable unpatented items; (b) the highway agency must certify that they are essential for synchronization with existing highway facilities for that no equally suitable alternative exists or; (c) they must be used for research or for a distinctive type of construction on relatively short sections of road for experimental purposes. Our regulations concerning proprietary products are contained in Title 23, Code of Federal Regulations, Section 635.411, a copy of which is enclosed.
The conditions in our letter of September 18, 1996 continue to apply.
Dwight A. Horne
Director, Office of Highway Safety Infrastructure