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                Safety Eligibility Letter B-182
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-182
                          **Date:**
            11/14/2008
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            MWRSF
                          **Device Description:**
            Concrete Median Barrier meeting head ejection criteria
                          **View PDF:**
            b182.pdf (1.56 MB)
    
    Safety Eligibility Letter B-182

			 
			**Download Version**PDF [1.56 MB]
			
			DOT logoU.S. Department of Transportation**Federal Highway Administration**
			1200 New Jersey Ave. S.E.Washington, D.C. 20590
			November 14, 2008
	  In Reply Refer To: HSSD/B-182
			
			Mr. Scott K. Rosenbaugh  
		    Research Associate Engineer
		    Midwest Roadside Safety Facility
		    University of Nebraska-Lincoln
		    527 Nebraska Hall  
		    Lincoln, Nebraska 38588-0529
            Dear Mr. Rosenbaugh:
            This letter is in response to your request for the Federal Highway Administration (FHWA)  acceptance of a roadside safety system for use on the National Highway System (NHS
      Name of  system:
                Vertical-Faced, Concrete Median Barrier Incorporating Head Ejection CriteriaType of  system:Concrete Median BarrierTest Level:
        NCHRP Report 350 TL 5 & MASH-08 TL 5Testing  conducted by:Midwest Roadside Safety FacilityDate of request:
                February 27, 2008Date of completed package:
                  October 14, 2008You requested that we find this system acceptable for use on the NHS under the provisions of  National Cooperative Highway Research Program (NCHRP) Report 350 “Recommended  Procedures for the Safety Performance Evaluation of Highway Features” and the proposed  American Association of State Highway and Transportation Officials’ Manual for Assessing  Safety Hardware 2008 (MASH-08).
      **Requirements**
      Roadside safety systems should meet the guidelines contained in the NCHRP Report 350,  "Recommended Procedures for the Safety Performance Evaluation of Highway Features".  FHWA Memorandum “ACTION: Identifying Acceptable Highway Safety Features” of  July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers.  You have also chosen to anticipate the adoption of MASH-08, an option that FHWA has offered  with the understanding that additional testing may need to be done if changes to the test criteria  are made before MASH-08 is formally adopted.
      **Description**
      This concrete median barrier is intended to safely redirect vehicles ranging from small cars to  fully-loaded tractor trailers, while (1) maximizing stability in passenger vehicles by limiting  wheel climb and roll, (2) addressing occupant safety by limiting peak impact forces,  (3) preventing head slap, and (4) providing an economical alternative to existing concrete barrier  designs. The profile of the upper 8 inches of the barrier is set back to accommodate a “head  ejection envelope” which was determined through an analysis of previous full-scale crash tests  involving passenger vehicles impacting vertical-faced barriers and other rigid concrete barriers.
      The geometry of this setback directly applies only to rigid barriers with a vertical or near vertical  face, and for belted occupants meeting the measurements of the Hybrid III 50 and 95 percentile  male dummies.  The final barrier cross section design is shown in the drawings which are enclosed for reference.  Also shown is the barrier end section with a footer whose function is to provide sufficient torsion  resistance to match the overturning moment of the end section.

            **Crash Testing**
            Full-scale crash testing was conducted with a tractor-trailer rig having a test inertial weight of  36,154 kg (79,538 pounds) following NCHRP Report 350 Test 5-12 and MASH-08 Test 5-12.  The enclosed test data summary page shows the impact velocity was 84.9 km/hr (55.7 mi/hr) at  an angle of 15.4 degrees. During the impact, the maximum roll angle of the truck was  22.8 degrees. Although the dynamic deflection of the barrier was negligible (38 mm, or about  1.5 inches), the “working width” considering the incursion of the box over the top of the barrier  was 1894 mm (75 inches).
            **Findings**
The concrete median barrier adequately contained and redirected the vehicle without permanent  displacements of the barrier. Vehicle roll, pitch, and yaw angular displacements were deemed  acceptable, because they did not adversely influence occupant risk safety criteria nor cause  rollover. After collision, the vehicle rode down the face of the barrier and did not intrude into  adjacent traffic lanes. Thus, the vehicle’s exit angle was less than 60 percent of the impact angle.  Therefore, test TL5CMB-2 conducted on a concrete median barrier was determined to be  acceptable according to the TL-5 safety performance criteria found in NCHRP Report 350. Note,  the test also satisfies all evaluation criteria for test 5-12 found in MASH-08.
            Therefore, the system described above and detailed in the enclosed drawings is acceptable for  use on the NHS under the range of conditions tested, when such use is acceptable to a highway  agency.
            As NCHRP Report 350 does not have mandatory evaluation criteria regarding vehicle occupants  contacting the hardware outside of the occupant compartment, this letter is limited to accepting  the performance as a median barrier to contain and redirect vehicles, with no implication that  head ejection criteria is a requirement. However, MASH-08 does identify the safety risk  involved with occupants extending out of the vehicle and coming into direct contact with the test  article in Section 4.2.1.5, Paragraph 2. This guidance recommends that dummies are to be placed in the front seat on the impact side of passenger vehicles during tests of longitudinal  barriers taller than 33 inches. Although a passenger vehicle test was not performed, the barrier  geometry was designed to prevent such occupant-barrier contact.
      Please note the following standard provisions that apply to the FHWA letters of acceptance:
            This acceptance 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 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 the NCHRP   Report 350.
              To prevent misunderstanding by others, this letter of acceptance is designated as number   B-182 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 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 acceptance letter 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.Sincerely yours,
						*/signed for*/
						David A. NicolDirector, Office of Safety DesignOffice of SafetyEnclosures U.S. DEPARTMENT OF TRANSPORTATION

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