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

Dear Mr. Leahy:

Thank you for your July 19, 2001, letter requesting Federal Highway Administration (FHWA) acceptance of a modification to our previous action on your company's SB8 slip base. We had previously found your "SB8" breakaway slip bases acceptable for single post supports on September 18, 1996 (Geometric and Roadside Design Acceptance Letter SS-68) and for dual and triple post supports on December 20, 1996 (SS-68A). These designs used triangular plates measuring 8 inches (203 mm) on a side.

Your present request is that the SB8 base, with a revised concrete foundation, be found acceptable for use on the National Highway System (NHS) under the provisions of National Cooperative Highway Research Program (NCHRP) Report 350 "Recommended Procedures for the Safety Performance Evaluation of Highway Features." You submitted calculations showing the increased depth necessary to compensate for the smaller diameter concrete foundation in weak soil.

Introduction

Testing of breakaway supports is to conform with the guidelines contained in the NCHRP Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. Requirements for breakaway supports are those in the American Association of State Highway and Transportation Officials' (AASHTO) Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals.

In light of the engineering analysis of the strength of soil necessary to adequately support the sign installation the FHWA concurs in your request to reduce the concrete footing diameter to 18 inches and increase the depth to 42 inches when used in weak soil (the worst case soil condition.) Therefore the devices described above and shown in the enclosed drawings for reference are acceptable for use as Test Level 3 devices on the NHS under the range of conditions tested, in either strong or weak soil, when proposed by a State.

Please note the following standard provisions which apply to FHWA letters of acceptance:

• Our acceptance is limited to the crashworthiness characteristics of the devices and does not cover their structural features, nor conformity with the Manual on Uniform Traffic Control Devices.
• Any changes that may adversely influence the crashworthiness of the device will require a new acceptance letter.
  
  
• Should the FHWA discover that the qualification testing was flawed, that in-service performance reveals unacceptable safety problems, or that the device being marketed is significantly different from the version that was crash tested, it reserves the right to modify or revoke its acceptance.
  
  
• You will be expected to supply potential users with sufficient information on design and installation requirements to ensure proper performance.
  
  
• You will be expected to certify to potential users that the hardware furnished has essentially the same chemistry, mechanical properties, and geometry as that submitted for acceptance, and that they will meet the crashworthiness requirements of FHWA and NCHRP Report 350. To prevent misunderstanding by others, this letter of acceptance, designated as number SS-68H shall not be reproduced except in full. As this letter and the supporting documentation which support it become public information, it will be available for inspection at our office by interested parties.
  
  
• The SB8 slip base is or will be a patented product and is considered "proprietary." The use of proprietary devices specified on Federal-aid projects, except exempt, non-NHS projects: (a) must be supplied through competitive bidding with equally suitable unpatented items; (b) the highway agency must certify that they are essential for synchronization with existing highway facilities or 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.

Sincerely yours,

Michael L. Halladay .

Acting Program Manager, Safety

Enclosure