U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000


Skip to content
FacebookYouTubeTwitterFlickrLinkedIn

Safety

eSubscribe
eSubscribe Envelope

FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter B-222

Download Version
PDF [755 KB]

DOT logo
U.S. Department of Transportation
Federal Highway Administration

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

January 27, 2012

In Reply Refer To:
HSST/B-222

Mr. Dallas James
Armorflex International Ltd
156 Foundry Road
Silverdale 0932
Auckland
New Zealand

Dear Mr. James:

This letter is in response to your request for the Federal Highway Administration (FHWA) to review a roadside safety system for eligibility for reimbursement under the Federal-aid highway program.

Name of system:

Armorwire

Type of system: Cable Barrier with 3 or 4 Cable
Test Level: NCHRP Report 350 TL-3 & TL-4
Testing conducted by: Holmes Solutions Ltd (HSL)
Date of request: December 15, 2010
Date initially acknowledged:

December 17, 2010

Task Force 13 Designator: SGM33 a-b

Decision:
The following device is eligible, with details provided below:

Based on a review of crash test results submitted by the manufacturer certifying the device described herein meets the crashworthiness criteria of the National Cooperative Highway Research Program (NCHRP) Report 350, the device is eligible for reimbursement under the Federal-aid highway program.  Eligibility for reimbursement under the Federal-aid highway program does not establish approval or endorsement by the FHWA for any particular purpose or use.

The FHWA, the Department of Transportation, and the United States Government do not endorse products or services and the issuance of a reimbursement eligibility letter is not an endorsement of any product or service.

Requirements
Roadside safety devices should meet the guidelines contained in NCHRP Report 350 (Report 350) if tested prior to January 1, 2011, 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”, dated July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers.

Description
The Armorwire systems use either 3 (for TL-3) or 4 (for TL-4) 19 millimeters (¾-inch) 3 x 7 strand galvanized pre-stretched cable with a breaking strength in excess of 227kN. The lower 3 cables are the same configuration for each system with cable heights of 530 millimeters (20.8 inches), 650 millimeters (26.0 inches) and 770 millimeters (30.3 inches) to the centre of the cable from ground level. For the 4 cable system, a second cable is added to the top slot in the post at a height of 790 millimeters (31.1 inches) from ground level. The cables are housed in galvanized steel, flat sided oval posts 1220 millimeters (48 inches) long and 3 millimeters (⅛-inch) thick. Once connected to the appropriate terminal ends, the system is tensioned to a nominal 25kN (5,600 pounds) at 21˚C (70˚F).  Each post has a notch on each side and 1 slot cut into the top of the post. All posts used in the Armorwire cable barrier are installed in 350 millimeters (13.8 inches) deep plastic sockets cast into concrete foundation piles 300 millimeters (11.8 inches) in diameter by 750 millimeters (29.5 inches) deep.  The soil was AASHTO 'standard' soil.  Drawings of both Armorwire designs are provided as an enclosure to this correspondence.

Crash Testing
The following four (4) tests for a re-directive cable barrier as per Report 350 TL-3 and TL-4 were conducted. The barrier was anchored using the ATE-4 cable terminal which was previously   accepted by the FHWA Letters CC-105 and CC-105A as either a 3 or 4 cable terminal end.

The crash test summary sheets are included as an enclosure to this correspondence.

Findings
The systems described above passed all required Report 350 crash tests. Occupant Impact Velocities (OIV) associated with all tests are below the preferred limit and Occupant Ridedown Acceleration (ORA) for all tests were below the preferred limit.

In your letter, you requested FHWA review of the following configurations for the Armorwire as an NCHRP 350 TL-3 and TL-4 Longitudinal Barrier:

  1. Armorwire TL-3 Cable Barrier – 3-cable system, for use with post spacing of 3 meters (9.83 feet) through to 9 meters (29.6 feet).
  2. Armorwire TL-4 Cable Barrier – 4-cable system, for use with post spacing of 3-meters 9.83 feet) through to 9 meters (29.6 feet).

We concur that the 3-cable design described above and detailed in the enclosed drawings is eligible for reimbursement as an NCHRP Report 350 barrier at TL-3 with a post spacing ranging from 3 meters (9.84 feet) to 9 meters (29.53 feet) under the range of conditions tested, when such use is acceptable to a highway agency. We further agree that the 4-cable design is eligible for reimbursement as an NCHRP Report 350 barrier at TL-4, but only with the 3 meters (post spacing that was actually tested. Based on that one test, there is no reliable method by which the dynamic deflection of the system with 9 meters post spacing can be accurately predicted for an impact with the single-unit truck. A secondary concern is that with large barrier deflections over non-level (sloping terrain), a high center of gravity vehicle is more likely to overturn, rather than be contained and redirected.

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

 

Sincerely yours,

/* Signature of Michael S. Griffith */

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

Enclosures

Page last modified on June 24, 2011.
Safe Roads for a Safer Future - Investment in roadway safety saves lives
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000