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                Safety Eligibility Letter B-157
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-157
                          **Date:**
            04/23/2007
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            Trinity Highway Products
                          **Device Description:**
            CASS TL-4 Cable Barrier system & terminal
                          **View PDF:**
            b157.pdf (619.42 KB)
    
    HSSD/B-157


DOT logo
U.S. Department of Transportation
**Federal Highway Administration**
400 Seventh St., S.W.
Washington, D.C.  20590April 23, 2007
In Reply Refer To:  
HSSD/B-157

Mr. Stephen L.  Brown, President
Trinity Highway Products, LLC
P.O. Box 568887
Dallas, Texas 75356-8887
	
Dear  Mr. Brown:
Thank you for your company’s letter of March 20, 2007,  requesting the Federal Highway Administration (FHWA) acceptance of  modifications to the CASS-TL-4 cable barrier system and the CASS Cable  Terminal. Accompanying your letter were  drawings of the modified barrier and terminal.  You requested that we find these devices acceptable for use on the  National Highway System (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.”
In the FHWA acceptance letter B-141 dated November 17, 2005,  the FHWA accepted the 
  3-cable CASS-TL-4 Cable Safety System to test level 4 (TL-4)  criteria. Your current request is to modify that barrier and terminal design to  incorporate a fourth cable at a height of 640 mm 
(25-3/16 inch), midway between the bottom and middle cables  of the original TL-4 CASS.
You also requested a modification to the NCHRP Report 350  TL-3 compliant terminal to accommodate the fourth cable. The modification includes increasing the  length of the CASS Cable Terminal through the addition of a fourth Cable  Release Post as shown in the enclosed drawing.  The fourth cable remains at the 640 mm height on the traffic side of the  terminal from post #9 through post #4, at which point it begins to descend towards  its terminus at Cable Release Post #1X.
You requested that the CASS-TL-4 Cable Safety System be  acceptable with post spacings from 2.0m (6.5 feet) to 9.9m (32.5 feet) and with  the same range of post embedment types (direct driven, set in driven tube, set  in tube sleeve in concrete foundation.)
**Testing**
Full-scale automobile testing documented under earlier  acceptance letters was conducted on 100m (334-foot) long installations of the  CASS-TL-3 Cable Safety System with cables spaced at 2m (6.5 feet), 6m (20 feet)  and 9.9m (32.5 feet). The cables were  not pre-stretched, but were tensioned to 5,600 pounds force for the test. The dynamic deflection for the 100m (330-foot)  long test installations were 1.6m (5.3 feet) for the 2m post spacing, 2.3m (7.7  feet) for the 6m post spacing and 3.4m (11.2 feet) for the 9.9m post spacing.
Although the barrier performed well under ideal test impact  conditions with the pickup truck, 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 100m (330-foot) test  length.
In spite of the above caveat, the modification to the CASS  TL-4 design described above using 
  4 cables may be used as either a roadside or median barrier on  the NHS when such use is acceptable to the contracting agency. Although the cables used in the test were not  pre-stretched, this acceptance is also valid if and when pre-stretched cables  are used, assuming that the recommended post-tensioning is applied to the  cables. The modified CASS-TL-4 end  terminal is likewise found to be acceptable.
**Findings**
  Because the addition of the fourth cable and associated  terminal hardware is not considered to be detrimental to the performance of the  crash tested system, and is indeed likely to increase the capacity and improve  the performance, the CASS-TL-4 devices 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 proposed by a State.
Please note the following standard provisions that apply to the  FHWA letters of acceptance:
Our acceptance is limited to the crashworthiness  characteristics of the devices.
  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 marketed is significantly different from the  version that was crash tested, 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.
  You will be expected to certify to potential  users that the hardware furnished has essentially the same chemistry,  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-157 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.
  The CASS barrier and terminal are patented  devices and considered "proprietary."  The use of proprietary devices *specified by a highway agency* for  use on Federal-aid projects must meet one of the following criteria: (a) it  must be supplied through competitive bidding with equally suitable unpatented  items; (b) the highway agency must certify that it is essential for  synchronization with existing highway facilities or that no equally suitable  alternative exists or; (c) it 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, a copy of which is enclosed.
  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.
			for:
			  John R. Baxter, P.E.
			  Director, Office of Safety Design
		    Office of SafetyEnclosures U.S. DEPARTMENT OF TRANSPORTATION

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