Refer to: HSA-10/SS-17C
Mr. Michael S. Stenko
President, Transpo Industries, Inc.
20 Jones Street
New Rochelle, New York 10801-6098
Dear Mr. Stenko:
Thank you for your letter of July 10, 2003, requesting Federal Highway Administration (FHWA) acceptance of an additional signpost to be used with your company's Type A Break Safe System as a breakaway sign support system for use on the National Highway System (NHS). Accompanying your letter were copies of previous correspondence regarding the Type A system. You requested that we find Type A Break Safe couplers with steel pipe posts acceptable for use on the NHS under the provisions of National Cooperative Highway Research Program (NCHRP) Report 350 "Recommended Procedures for the Safety Performance Evaluation of Highway Features."
Testing of Type A Break Safe couplings on structural steel supports was conducted in compliance 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' Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals.
Type A Break Safe couplings were the subject of our Acceptance Letters SS-17, SS17-A, and SS-17B, dated January 8, 1990, March 7, 1995, and April 25, 1995 respectively.
Your request was for the use of Schedule 40 steel pipe sign posts supported on the Type A Break Safe coupling. The diameter of the post will be a minimum of 3 inches. Modifications to your Type A coupling to accommodate a round pipe include an adaptor as shown in the enclosed drawing for reference.
Your analysis comparing the crash-tested 4 pound-per-foot u-channel sign support to the 3 inch schedule 40 pipe via plastic design method shows that the 3 inch diameter steel pipe is strong enough to transfer the force of the impact directly to the couplings without deforming. Therefore, the Type A Break Safe Couplings for 3 inch and larger OD pipes 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, when proposed by a State.
Please note the following standard provisions that apply to FHWA letters of acceptance:
Michael S. Griffith
Acting Director, Office of Safety Design
Office of Safety