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                Safety Eligibility Letter CC-68A
  
  **Hardware Type:**
            Barrier Terminals and Crash Cushions
                          **Code:**
            CC-68A
                          **Date:**
            08/19/2011
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            MWRSF
                          **Device Description:**
            TL-3 Thrie Beam Bullnose with UBSP
                          **View PDF:**
            cc68a.pdf (352.44 KB)
    
    Safety Eligibility Letter CC-68A



			 

			**Download Version**PDF [60 KB]

			

			DOT logoU.S. Department of Transportation**Federal Highway Administration**

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

			August 19, 2011

			In Reply Refer To: HSST/CC-68A

			

	 Mr.  Dean L. Sicking, Ph.D., P.E. Director, 
	   Midwest Roadside Safety Facility University
of Nebraska - Lincoln P.O. Box 880601
Lincoln, NE 68588-0601
This  letter is in response to Messrs. Bielenburg's and Faller's request for the  Federal Highway Administration  (FHWA) acceptance of an alternative post design for the Thrie beam bullnose  median barrier (bullnose attenuator) for use on the National Highway System  (NHS).
Name of system:

					Thrie beam bullnose guardrail systemType of system:

					Non-Gating Crash Cushion/Impact AttenuatorTest Level:

					NCHRP Report 350 Test Level 3Testing conducted by:

					Midwest  Roadside Safety Facility.Date of request:

					December 21, 2010Request Initially acknowledged:

					December  22, 2010Task Force 13 designator:

					SET03bYou  requested that we find a steel post design to be an acceptable alternative to  the previously-accepted  wood post Thrie beam bullnose attenuator for use on the NHS under the provisions of the National Cooperative  Highway Research Program (NCHRP) Report 350.
    **Requirements**
      Roadside  safety devices should meet the guidelines contained in NCHRP Report 350 if  tested prior to January 1, 2011, and the guidelines in American Association of  State Highway Transportation  Official's (AASHTO) Manual for Assessing Safety Hardware if tested after that  date. The FHWA memorandum "ACTION: Identifying Acceptable Highway Safety  Features" of July  24, 1997, provides further guidance on crash testing requirements of  longitudinal barriers and crash cushions.
    **Decision**
      The following device was found acceptable, with details  provided below:
    Thrie beam Bullnose Barrier with Universal Breakaway Steel Posts (UBSP)**Description**
      The  steel post design of the bullnose attenuator is essentially identical to the  original wood post design that was accepted for use on the NHS in FHWA  acceptance letter CC-68, dated November 8, 2000. The design consists of five **slotted**Thrie beam rail elements: the nose piece with a 1580-mm (62-3/16-inch)  radius, two sections (one on each end of the nose section) with 10400-mm (409-7/16-inch) radii, and  one straight rail section on each end of the second sections. Two 5/8-inch diameter steel cables  are set behind the top two corrugations in the nose piece. Posts 1 and 2 are  wood BCT-type posts and effectively anchor the bullnose in side impacts. In the modified design, the original CRT  posts (numbered 3 through 8) have been replaced with the new UBSP. The lower section of the  UBSP consists of a 6 inch x 8 inch x 3/16 inch ASTM A500 Grade B steel  foundation tube with the lower base plate. The upper portion of the UBSP is a  W6 x 8.5 post with the upper base plate. The plates are connected with  7/16-inch diameter ASTM A325 threaded hex bolts. Drawings showing the overall  layout of the Bullnose design and the UBSP  posts are shown in Enclosure **1.**
    **Crash Testing**
      Since  the UBSP design of the bullnose attenuator was essentially unchanged from the  previously accepted CRT  post version, you needed only to show that the new post system would not adversely affect the crash performance  of the unit. You concluded that NCHRP Report 350 tests 3-30,3-31, and 3-38 were those most  likely to be effected by the post substitution and that the remaining tests for a redirective  crash cushion need not be rerun. After discussing the test matrix with Mr.  Bielenberg, FHWA agreed that the remaining tests would be redundant and  accepted the three tests described below as adequate and sufficient to verify  crashworthiness of the UBSP design.
    **Test  3-30**required a 100  km/h impact by a 1800 lb (820-kg) passenger car impacting at 62 mph (100 km/h)  directly into the nose of the barrier with a 1/4-point offset. In test no.  USPBN-3, the car was  captured by the bullnose with little roll or pitch. As shown in Enclosure 2,  maximum occupant impact velocity was 33.6 feet/s (10.2 m/s) and the ridedown  acceleration was 7.7 g's. The vehicle was brought to a stop approximately 21 ft  from the first impact point.
    **Test****3-31** was run as test no. USPBN-4 and consisted of a 4429-lb (2009-kg)  pickup truck impacting  the Bullnose Attenuator head-on at 64.5 mph (103.7 km/h). The truck was  captured by the barrier and brought to a stop in approximately 51 feet.  Occupant Impact Velocity (OIV) was reported to be 21.8 feet/s (6.6 m/s) and the maximum acceleration  was under 8 g's. Enclosure 3 is the summary  sheet for this test.
    **Test  3-38**also required a  100 km/h 2000-kg pickup truck test, but into the side of the Bullnose Attenuator at its critical impact  point (CIP).  The Midwest Roadside Safety  Facility test number USPBN-2 reported a 2029-kg (4472-lb) truck struck the  barrier at 101.3 km/h (62.9 km/h) and 21.7 degrees. The OIV was 8.6 m/sec (longitudinal) and  the Ridedown Acceleration was approximately 15 g's. Vehicular roll, pitch and yaw were recorded as  12.6, 5.9, and 20.7 degrees,  respectively. The truck came to rest within the bullnose envelope, 28 feet (8.7  m) downstream from the initial impact point. Enclosure 4 is the summary sheet  for this test.
    **Findings**
      The Thrie beam Bullnose Attenuator with UBSP as  described above is acceptable for use on the NHS as a non-gating crash cushion primarily used to  shield rigid objects located in the medians of divided highways. 
      The conditions listed in the original acceptance letter  remain in effect and are repeated here for  ready reference:
    The  leading edge of the bullnose should be installed a minimum distance of 19 m in advance of any shielded object or hazard.
      If  transitioned to a bridge railing or parapet, the transition should begin no  sooner than post 9, measured from the nose of  the installation
      If  an asymmetrical design is used (refer to CC-68 for details), the barrier flare  rates on the approaching traffic side should not exceed the AASHTO Roadside  Design Guide recommendations
      The  bullnose attenuator should be installed on relatively flat ground (e.g. 10H:1V  or flatter) to ensure optimal crash  performance.Please  note the following standard provisions that generally apply to all FHWA letters  of acceptance:
    This  acceptance letter includes an AASHTO/ARTBA/AGC Task Force 13 designator that should be used when creating a new or  revised Task Force 13 drawing.
      This  acceptance is limited to the crash worthiness characteristics of the systems  and does not cover their  structural features, nor conformity with the Manual on Uniform Traffic Control Devices (when applicable).
      Any  changes that may adversely influence the crashworthiness of the system 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 system being  marketed is significantly  different from the version that was crash tested, we reserve the right to modify or revoke our 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 NCHRP  Report 350.
      To  prevent misunderstanding by others, this letter of acceptance is designated as  number CC-68 A 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.
      The  Thrie beam Bullnose Attenuator is not a patented product, nor is it considered  proprietary. However, if any proprietary devices are specified by a highway  agency for use on  Federal-aid projects, except exempt, non-NHS 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.
      This acceptance 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 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 Michael S. Griffith */*
			      
			      Michael S. GriffithDirector, Office of Safety TechnologiesOffice of SafetyEnclosures U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

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