Federal Highway Administration
400 Seventh St., S.W.
Washington, D.C. 20590
March 9, 2006
Mr. Jim Anderson
7339 Wildwood Road
Stillman Valley, IL 61084
Dear Mr. Anderson:
This is in response to Mr. William Williams’ letter of March 2, 2006, requesting the Federal Highway Administration’s (FHWA) acceptance of a modification to the Designovation Snap-N-Safe breakaway coupler for use with sign support systems on the National Highway System (NHS). Accompanying your letter was a letter report on the pendulum test conducted by the Texas Transportation Institute. Mr. Williams requested that we find the Designovation device 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 the supports was 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' (AASHTO) Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals.
Full-scale automobile testing was conducted on the original Designovations Snap-N-Safe grey iron breakaway coupler in 2004. This design was found acceptable in the FHWA acceptance letters numbered SS-120 (larger coupler) and SS-123 (smaller coupler), dated April 1, 2004.
The present modification of the 2-½ inch square version consists of a coupler and mounting plate manufactured from a single grey iron casting. This design is intended for bolting directly to concrete surfaces such as sidewalks and medians. Testing using an 839-kg pendulum with a honeycomb impact nose was conducted. The 2-1/2 inch device was attached to a rigid steel plate on the pendulum platform. The tested is shown in the Enclosure for reference.
|Test #||NCHRP 350||Speed||Article||Occup. Speed|
|400001-DES-P||Test 3-61||34.7 km/hr||Snap N Safe||2.3 m/s|
Occup. Speed: Occupant Impact Speed: Speed at which a theoretical front seat occupant will contact the windshield. In meters per second.
Delta V: Speed change of the test vehicle. In meters per second.
Velocity change was within acceptable limits, and the stub remaining was approximately 16 mm (5/8 inch). The results of testing met the FHWA requirements and, therefore, the devices described above and shown in the enclosed drawings for reference, as well as the smaller square sizes of 2 1/4", 2" and 1 3/4", 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 the FHWA letters of acceptance:
John R. Baxter, P.E.
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