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                Safety Eligibility Letter B-161
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-161
                          **Date:**
            07/03/2007
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            NYSDOT
                          **Device Description:**
            Generic 4-strand cable barrier system
                          **View PDF:**
            b161.pdf (849.9 KB)
    
    HSSD-10/B-161


DOT logo
U.S. Department of Transportation
**Federal Highway Administration**
400 Seventh St., S.W.
Washington, D.C.  20590July 12, 2007
In Reply Refer To:  
HSSD-10/B-161

Mr. Pratip Lahiri, P.E.
Specifications and  Standards Section, POD 23
New York State  Department of Transportation
50 Wolf Road 
Albany, NY 12232
	
Dear Mr. Lahiri:
Thank you for your letter requesting the Federal Highway  Administration’s (FHWA) acceptance of a four strand cable median barrier as a  Test Level 3 device for use on the National Highway System (NHS). The median barrier is a modification of your  previously accepted generic three strand cable system. You requested that we find this barrier  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.”
**Introduction**
  The FHWA guidance on crash testing of roadside safety  hardware is contained in a memorandum dated July 25, 1997, titled “INFORMATION:  Identifying Acceptable Highway Safety Features.”
**Testing**
  Generic low-tension 3-cable barriers have been tested with  various cable heights and spacing. The New York State Department of  Transportation cable median design has the top cable at 
  28 inches above grade with the cables spaced 6 inches  apart. The Federal Outdoor Impact  Laboratory recently conducted physical testing and computer simulations of  cable median barrier designs. These  indicated a need for the bottom cable to be significantly lower than most  designs currently in use. Your  modification is in conformance with the recommendations of that research. Those recommendations indicated a need for  the cable median barrier to have four cables, spaced 6 inches apart vertically,  and mounted on alternating sides of the post with the lowest cable on the  downhill side.
You acknowledged various limitations on the use of cable  barrier systems. Once struck, the entire  run is effectively compromised until the damage is repaired and the system  retensioned. Winter repairs are often deferred until spring due to the  inability to drive replacement posts in the frozen ground.
Cable tension under varying temperature conditions, and  spacing between anchorages are detailed on the drawings.
Old installations used a 1 cubic yard anchor block that sometimes  moved after several impacts. You doubled the block size and added a check of  the anchor block orientation to your impact repair procedure to ensure that anchor  blocks do not rotate enough that a cable end is released from its anchor angle  slot.
**Findings**
  Your request to add a fourth cable to your median barrier  system includes a separate anchor connection for the added cable. This connection is identical to the  connections for the other three cables and can be expected to perform in a  similar manner. Because the addition of  a fourth cable will serve to improve the performance of your median barrier  system, with little potential for any adverse consequences, the system  described above and detailed in the enclosed drawings is acceptable for use on  the NHS as a test level 3 device.
Please note the following standard provisions that apply to the  FHWA letters of acceptance:
This acceptance is limited to the  crashworthiness characteristics of the device(s).
  Any changes that may adversely influence the  crashworthiness of the device will require a new acceptance letter.
  Should the FHWA discover that the qualification  testing was flawed, that in-service performance reveals unacceptable safety  problems, or that the device being installed is significantly different from  the accepted version, it reserves the right to modify or revoke its acceptance.
  You will be expected to supply potential users  with sufficient information on design and installation requirements to ensure  proper performance.
  It is expected that the hardware furnished will  have essentially the same mechanical properties, and geometry as that submitted  for acceptance, and that it will meet the crashworthiness requirements of the  FHWA and the NCHRP Report 350.
  To prevent misunderstanding by others, this  letter of acceptance, designated as number B-161 shall not be reproduced  except in full. This letter, and the  test documentation upon which this letter is based, is public information. All such letters and documentation may be  reviewed at our office upon request.
  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.Sincerely yours,
			Signature of George E. Rice, Jr.
			George E.  Rice, Jr.
Acting  Director, Office of Safety Design
Office  of Safety3 Enclosures U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

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WASHINGTON, DC 20590

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