Skip to contentUnited States Department of Transportation - Federal Highway Administration FHWA HomeFeedback

October 7, 1997

Refer to: HNG-14/SS-68B

Mr. Lawrence E. Leahy
Xcessories Squared
P.O. Box 135
Auburn, IL 62615

Dear Mr. Leahy:

This is in response to your August 8 letter to Mr. Nicholas Artimovich requesting that your company's Xcessories Squared slip-base components be found acceptable when used with an existing three-bolt triangular slip base anchor plate.

Our acceptance letter SS-68, dated September 18, 1996, found your company's slip base acceptable for use on the National Highway System (NHS) when used with a single 63.5 mm square, 12 gage perforated steel tube sign support and a foundation tube with a soil plate or a concrete foundation.

We concur with your assessment that the components of the system can be expect to perform in an acceptable manner when used with an existing compatible triangular slip base. Therefore, they will e acceptable for use on existing foundation slip plates on the NHS, subject to the following conditions.

  1. The foundation slip plate and the support mass are similar to those crash tested. (A drawing of the tested system is enclosed for reference. Critical components of crashworthy slip bases are the clamping force in the splice bolts, the size (angle) of the notch to receive the splice bolts, the thickness and material properties of the slip plates, and the finish of the surfaces, both those of the throats of the notches and those of the parallel slip surfaces. Care must be exercised to ensure that Xcessories Squared components used with an existing foundation slip plate are compatible and create a slip base comparable to that tested.)
  2. The foundation anchor is at least as firm as the crash-tested installation covered in our acceptance letter SS-68. (In that installation the stub in strong soil was affixed with a soil plate, as in the enclosure. Your standard concrete foundation would, of course, also be acceptable.
  3. All hardware in the slip base except the foundation slip plate is replaced by the Xcessories Squared hardware kit, including a Teflon bolt retainer gasket and two stainless steel release bushings on each splice bolt.

Should you have any questions, please do not hesitate to call Mr. Artimovich at (202) 366-1331.

Sincerely yours,

Dwight A. Horne, Chief
Federal-Aid and Design Division


Supplemental Geometric and Roadside Design Acceptance Letter SS-68B

FHWA Safety Home | FHWA Home | Feedback
United States Department of Transportation - Federal Highway Administration