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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter SS-165

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U.S. Department of Transportation
Federal Highway Administration

1200 New Jersey Ave. S.E.
Washington, D.C. 20590

January 21, 2011

In Reply Refer To: HSSD/ SS-165

Mr. Jim Anderson
Designovations, Inc.
7339 Wildwood Road
Stillman Valley, IL 61084

Dear Mr. Anderson:

This letter is in response to your request for the Federal Highway Administration (FHWA) acceptance of revisions to roadside safety systems for use on the National Highway System (NHS).

Name of system: Snap’n Safe Couplers
Type of system: Breakaway Sign Support
Test Level: TL-3
Testing conducted by: N/A
Task Force 13 Designator: SSC12a, SSC15a
Date of request: March 26, 2010
Request acknowledged: April 1, 2010


    

You requested that we find these revised systems acceptable for use on the NHS under the provisions of the National Cooperative Highway Research Program (NCHRP) Report 350 “Recommended Procedures for the Safety Performance Evaluation of Highway Features.”

Decision
The modifications you requested to SS-136 and SS-146 are acceptable, as discussed below.

Requirements
Roadside safety devices should meet the guidelines contained in the NCHRP Report 350 or the American Association of State Highway and Transportation Officials’ Manual for Assessing Safety Hardware (MASH). Requirements for breakaway supports are those in the American Association of State Highway and Transportation Officials’ Standard Specifications for Structural Supports for Highway Signs, Luminaries and Traffic Signals.

Description
Snap ‘n Safe cast iron couplings were covered in the following FHWA Acceptance Letters:

FHWA Letter # Date of Letter Snap ‘ n Safe couplers covered
SS-156 12/6/2007 Round surface mount, u-channel surface, in-ground mount
SS-146 3/16/2007 Round coupler
SS-136 3/9/2006 Modifications for sizes 2 1/2 inches and smaller
SS-123# 2/28/2007 Coupling for square sign supports
SS-123 4/1/2004 System for fiberglass square tube sign
SS-120 4/1/2004 System for perforated square steel tube sign posts

Your first request updates the FHWA Acceptance letter SS-136 to include a new modified coupler for perforated square steel tube signposts to be mounted on angled surfaces. This coupler is identical to the previous coupler described in SS-136 with the addition of features that allow for angled surface mounting. This coupler is designed for use with 1 3/4", 2", 2 1/4", and 2 1/2" perforated square steel tube signposts and the NEX sign post. A detail drawing of the new modified coupler is enclosed for reference. The modification in design to this new surface mount SNAP‘n SAFE breakaway signpost coupler will not adversely affect the crashworthy performance of this device and it is acceptable for use on the National Highway System (NHS).

Your second request updates the FHWA Acceptance letter SS-146 to include a new modified coupler for round signposts. This coupler is identical to the previous coupler described in SS-146 with the only difference being the new modified coupler is designed for use with three inch diameter round signposts and the previous version is for 2 3/8 inch round signposts. A detail drawing of the new modified coupler is included. The modification in design to this new in ground SNAP‘n SAFE breakaway signpost coupler will not adversely affect the crashworthy performance of this device and it is acceptable for use on the National Highway System (NHS).

Crash Testing
No new crash testing was conducted in conjunction with this request. The frangible cross-section area of the modified couplings is equal to the original, crash tested couplers. Since the strength and stiffness of the sign posts is equal to or greater than the posts that were crash tested, the modified couplings can be expected to perform in an acceptable manner.

Findings
Modifications described in the requests above and detailed in the enclosed drawings are acceptable for use on the NHS under the range of conditions tested, when such use is acceptable to a highway agency.

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

 

Sincerely yours,

/* Signature of Michael S. Griffith */

Michael S. Griffith
Director, Office of Safety Technologies
Office of Safety

Page last modified on December 17, 2013.
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