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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter CC-109B

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U.S. Department of Transportation
Federal Highway Administration

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

August 17, 2011

In Reply Refer To: HSSD/CC-109B

Mr. Gerrit A. Dyke, P.E.
Barrier Systems, Inc.
3333 Vaca Valley Parkway, Suite 800
Vacaville, CA 95688

Dear Mr. Dyke:

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

Name of system: X-TENuator and X-TENuator Wide Backstop Extension
Type of system: Backstop Extension for X-TEN and X-TEN Wide Crash Cushions
Test Level: NCHRP Report 350 Test Level 3 (TL-3)
Testing conducted by: Safe Technologies Inc.
Date of request: December 29, 2010
Request Initially acknowledged: January 7, 2011
Task Force 13 designator: SCI23c X-TENuator Backstop Extension; and, X-TENuator Wide Backstop Extension

You requested that we find a backstop extension design used in conjunction with your X-TEN and X-TEN Wide crash cushions 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.” The original design width described in FHWA Acceptance letter CC-109 for your parallel-sided attenuator was 36-inches (926-millimeters) and the maximum width for your X-TEN Wide described in Acceptance letter CC-109A was 60-inches (1525-millimeters) wide.

Requirements
Roadside safety devices should meet the guidelines contained in the NCHRP Report 350 if tested prior to December 31, 2010 or the American Association of State Highway and Transportation Officials’ Manual for Assessing Safety Hardware (MASH) if tested after that date.  The FHWA Memorandum “Identifying Acceptable Highway Safety Features” of July 25, 1997 provides further guidance on crash testing requirements of longitudinal barriers.

Decision
The following system design was found acceptable, with details provided below:


 

Description
The X-TEN and X-TEN Wide systems are both redirective, non-gating crash cushion designed to decelerate an errant vehicle to a safe stop when struck end-on or redirect an errant vehicle away from roadside or median hazards when impacted along either side.  The systems are comprised of an energy absorbing nose bracket and cover, dual X-Tension impact heads and cables, front cable anchors, and W-Beam side panels.  The narrow X-TEN uses single posts or double support posts with braces, whereas the X-TEN Wide uses only the double row of specially designed posts and post braces.  Standard W-Beam offset blocks are used to attach the side panels to the posts.

The X-TEN Backstop Extension is intended for use with the X-TEN when hazards wider than 36 inches (926 millimeters) are encountered or with the X-TEN Wide for hazards greater than 60 inches (1525 millimeters) in width.  By separate correspondence, you indicated that the Backstop Extension would be marketed to shield hazards 48 inches, 60 inches, and 72 inches ( 1.2 meters, 1.5 meters, and1.9 meters ) wide when used behind the narrow, parallel-sided X-TEN, and 86 inches, 98 inches and 110 inches (2.2 meters, 2.5 meters, and 2.8 meters ) wide hazards when used with the X-TEN Wide unit.  The Backstop Extension (Enclosure 1) uses fabricated steel posts (Enclosure 2), variable-sized cross braces (Enclosure 3), and attachment brackets (Enclosure 4) in addition to standardized hardware items.

Crash Testing
Since both the X-TEN and the X-TEN Wide designs were fully crash-tested and accepted for use on the NHS by FHWA, only two tests were considered necessary to verify the crashworthiness of the X-TEN Backstop Extension.  Tests 3-36 and 3-38 were conducted with the Backstop Extension installed at its maximum 10-degree angle and connected to the narrow X-TEN design.  For both tests, the  system was attached to a 75-millimeter (3-inch) thick Asphalt Concrete (AC) pad over 300 millimeters (12 inches) of a dense graded aggregate with eighty-six (86) 20-millimeter (3/4-inch) long all thread studs embedded 400 millimeters(16 inches) and epoxied in place. Enclosures 5 and 6 summarize the results of these tests.

Findings
The FHWA concurs that the tests you ran were sufficient to verify acceptable crash performance under NCHRP Report 350 and that each test met the appropriate evaluation criteria.  In your letter, you have requested FHWA acceptance of the following:

Based on our review of the submitted information, including test reports, the X-TEN Backstop Extension described above and detailed in the enclosed drawings is 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:

CC-109B and shall not be reproduced except in full. This letter and the test documentation upon which it is based are public information. All such letters and documentation may be reviewed at our office upon request.

 

Sincerely yours,

/* Signature of Michael S. Griffith */
Michael S. Griffith
Director, Office of Safety Technologies
Office of Safety

Enclosures

Page last modified on January 17, 2013.
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