Safety Eligibility Letter B-222
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:
Mr. Dallas James
Armorflex International Ltd
156 Foundry Road
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:
|Type of system:
||Cable Barrier with 3 or 4 Cable|
||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:
The following device is eligible, with details provided below:
- Armorwire Cable Barrier with 3 or 4 Cable
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.
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.
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.
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.
- Test 4-10 was conducted with the 820C test vehicle on the 4 cable system which was 115 meters (377 feet) long including two 8 meters (26 feet) long Terminal Ends. The CIP was mid-span between posts 10 and 11, and the posts were installed on 3 meters (9.83 feet) centers in the impact area. The vehicle was smoothly re-directed by the barrier with all 4 cables remaining in contact with the impact side of the vehicle. The occupant risk values were all below the preferred limits. The dynamic deflection was 1280 millimeters (50.4 inches).
- Test 3-11 was conducted with the 2000P truck on the 3 cable system which was 130 meters (427 feet) long including two 8 meters (26 feet) long Terminal Ends. The CIP was 2 meters (6.56 feet) upstream of post 13, and the posts were again installed on 3 meters (9.83 feet) centers in the impact area. The vehicle was slowed and smoothly re-directed by the barrier. The occupant risk values were all below the Report 350 preferred limits. The dynamic deflection was 1540 millimeters (60.6 inches).
- Test 4-11 was not conducted since it is identical to test 3-11.
- Test 4-12 was conducted with the single-unit truck on the 4 cable system which was 130 meters (427-foot) long including two 8-meter (26-foot) long Terminal Ends. The CIP was at post 13, with the posts again installed on 3-meter (9-foot-10-inch) centers in the impact area. The vehicle was slowed and smoothly re-directed and captured by the barrier. The occupant risk values were all below the preferred limits. The dynamic deflection was 1650-millimeter (65.0-inch).
- Test 3-11 was conducted with the 2000P truck a second time on the 3 cable system which was 115 meters (377feet) long including two 8 meters (26 feet) long Terminal Ends. The CIP was mid-span between posts 10 and 11, this time with the posts installed on 9 meters (29.5 feet) centers in the impact area. The vehicle was smoothly re-directed and captured by the barrier with all 3 cables remaining in contact with the impact side of the vehicle. The occupant risk values were all below the preferred limits. The dynamic deflection was 3270 millimeters (128.7 inches).
The crash test summary sheets are included as an enclosure to this correspondence.
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:
- 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).
- 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:
- This letter provides a AASHTO/ARTBA/AGC Task Force 13 designator that should be used for the purpose of the creation of a new and/or the update of existing Task Force 13 drawing for posting on the on-line 'Guide to Standardized Highway Barrier Hardware' currently referenced in AASHTO Roadside Design Guide.
- This finding of eligibility is limited to the crashworthiness characteristics of the systems and does not cover their structural features, nor conformity with the Manual on Uniform Traffic Control Devices.
- Any changes that may influence the crashworthiness of the system will require a new reimbursement eligibility letter.
- Should the FHWA discover that the qualification testing was flawed, that in-service performance reveals safety problems, or that the system is significantly different from the version that was crash tested, we reserve the right to modify or revoke this letter.
- You will be expected to supply potential users with sufficient information on design and installation requirements to ensure proper performance.
- You will be expected to certify to potential users that the hardware furnished has the same chemistry, mechanical properties, and geometry as that submitted for review, and that it will meet the crashworthiness requirements of the NCHRP Report 350.
- To prevent misunderstanding by others, this letter of eligibility is designated as number B-222 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.
- This letter shall not be construed as authorization or consent by the FHWA to use, manufacture, or sell any patented system for which the applicant is not the patent holder. The finding of eligibility is limited to the crashworthiness characteristics of the candidate system, 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.
- The Armorwire systems are patented products and considered proprietary. If proprietary systems are specified by a highway agency for use on Federal-aid projects: (a) they must be supplied through competitive bidding with equally suitable unpatented items; (b) the highway agency must certify that they are essential for synchronization with the existing highway facilities or that no equally suitable alternative exists; or (c) they must be used for research or for a distinctive type of construction on relatively short sections of road for experimental purposes. Our regulations concerning proprietary products are contained in Title 23, Code of Federal Regulations, Section 635.411.
- Although the barrier performed well under ideal test impact conditions with the two test vehicles, the likelihood of passenger car underrides of any cable system may increase as the post spacing increases, particularly when the barrier is installed on non-level or slightly irregular terrain and the cables are not restrained from lifting at each post. Consequently, some transportation agencies have limited post spacing to approximately 6m (20 feet) for cable barriers. The dynamic deflection of the barrier is likely to increase when it is installed along the convex sides of horizontal curves, and when distances between anchorages exceed the 115- to 130-m (377- to 427-foot) test lengths.
/* Signature of Michael S. Griffith */
Michael S. Griffith
Director, Office of Safety Technologies
Office of Safety