Federal Highway Administration
1200 New Jersey Ave. S.E.
Washington, D.C. 20590
October 25, 2007
Mr. Jim Anderson
7339 Wildwood Road
Stillman Valley, IL 61084
Dear Mr. Anderson:
This letter is in response to your August 8,2007, correspondence requesting the Federal Highway Administration's (FHWA) acceptance of your company's three SNAP'n SAFE breakaway sign support couplers as the National Cooperative Highway Research Program (NCHRP) Report 350 Test Level 3 (TL-3) devices. The three devices are: (1) the SNAP'n SAFE Round Surface Mount Breakaway Coupler, (2) the SNAP'n SAFE U-Channel Surface Mount Breakaway Coupler, and (3) the SNAP'n SAFE U-Channel In Ground Breakaway Coupler. To support your request, you provided the Texas Transportation Institute (TTI) test report "Pendulum Testing of the Designovations Small Sign Support Breakaway Couplers" dated August 3,2007.
Sign supports should meet the guidelines contained in the NCHRP Report 350, "Recommended Procedures for the Safety Performance Evaluation of Highway Features." The FHWA Memorandum "ACTION: Identifying Acceptable Highway Safety Features" of July 25, 1997, provides further guidance on crash testing requirements of sign supports and on the use of low-speed pendulum tests as a surrogate for full-scale crash testing.
All of SNAP'n SAFE breakaway couplers are made from cast iron. The couplers are designed to break off at any impact angle. The SNAP'n SAFE Round Surface Mount Breakaway Coupler is used with 2-318 inch (60.3 mm) diameter round sign supports with wall thicknesses of 16 gauge (thin wall) up to and including 8 gauge (heavy wall). The SNAP'n SAFE U-Channel Surface Mount and In Ground Breakaway Coupler can be used with 2 lb, 2-112 lb, 3 lb, and 4 lb (0.91 kg, 1.13 kg, 1.36 kg, 1.81 kg respectively) U-channel posts. The design details of SNAP'n SAFE breakaway couplers are enclosed.
The NCHRP Report 350 criteria for sign supports to meet TL-3 suggests they must successfully pass tests 3-60 and 3-6 1. These tests involve an 820 kg passenger car impacting the support head-on at the critical impact angle, at a speed of 35 km/h (test 3-60) and 100 km/h (test 3-61). Alternatively, tests with pendulums are acceptable for most breakaway supports with the exceptions of base bending or yielding supports.
The following three pendulum tests were conducted to verify the performance of the couplers:
In addition, TTI extrapolated the high speed performance from the low speed pendulum tests. We agree that the test articles appear to perform appropriately to make such high speed extrapolations. The high speed extrapolations yielded equivalent or lower change in velocity values than the paired low speed pendulum tests.
We agree that the above tests are the most critical for your company's SNAPYnS AFE breakaway couplers and that successful performance in these tests indicates that the device should also perform acceptably with heavier sign posts. According to the information you provided, all three tests were successful in that the three SNAP'n SAFE breakaway sign support couplers met all of the applicable NCHRP 350 evaluation criteria. In the conducted tests the support separated from the base as designed. No intrusion into the occupant compartment occurred, and the maximum change in vehicle velocity was less than the permitted maximum limit of 16 ftjs (4.88 mls). Extrapolations fiom low-speed pendulum tests to high speed performance conducted by TTI have shown that the maximum change in velocity will likely be lower than indicated in all conducted pendulum tests. A summary of the test results is enclosed.
The damage sustained by the test articles was as follows:
In summary, we agree that the three SNAP'n SAFE Breakaway Couplers as described above meet the appropriate evaluation criteria for NCHRP 350 TL-3 devices, and may be used with small sign supports at all appropriate locations on the NHS when selected by the contracting authority, subject to the provisions of Title 23, Code of Federal Regulations, Section 635.41 1, as they pertain to proprietary products. Please note that this acceptance is based on the reported crash performance of the couplers and is not meant to address their installation, maintenance or repair characteristics.
Please note the following standard provisions that apply to the FHWA letters of acceptance:
This acceptance letter shall not be construed as authorization or consent by the FHWA to use, manufacture, or sell any patented device for which the applicant is not the patent holder. The acceptance letter is limited to the crashworthiness characteristics of the candidate device, and the FHWA is neither prepared nor required to become involved in issues concerning patent law. Patent issues, if any, are to be resolved by the applicant.
George E. Rice, Jr.
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