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                Safety Eligibility Letter B-156
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-156
                          **Date:**
            03/21/2007
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            Gregory Industries Inc.
                          **Device Description:**
            GMS-TB Guardrail System
                          **View PDF:**
            b156.pdf (2.53 MB)
    
    HSSD/B-156


DOT logo
U.S. Department of Transportation
**Federal Highway Administration**
400 Seventh St., S.W.
Washington, D.C.  20590March 21, 2007
In Reply Refer To:  
HSSD/B-156

Mr.  Andrew Artar
Vice  President Sales and Marketing 
Gregory  Industries, Inc.
4100  13th Street, SW
Canton,  OH 44170
	
Dear  Mr. Artar:
In  your letter of December 13, 2006, you requested the Federal Highway  Administration's (FHWA) acceptance of Single-Sided and Double Sided Thrie-Beam  called the GMS-TB Guardrail System at the National Cooperative Highway Research  Program (NCHRP) Report 350 test level 3 (TL-3). To support your request, your company sent a  copy of the Southwest Research Institute report dated November 30, 2006,  entitled "NCHRP Report 350 Test 4-11 Full-Scale  Crash Evaluation of a Single-face GMS-TB Guardrail System" and digital  videos of the crash test conducted on the GMS-TB Guardrail System. You also requested the waiver of tests 3-10  of the Single-Sided and Double Sided GMS-TB Guardrail System and test 3-11  of the Double-Sided GMS-TB Guardrail System.
**Requirements**
  Longitudinal  barriers should meet the guidelines contained in the NCHRP Report 350,  "Recommended Procedures for the Safety Performance Evaluation of Highway  Features.” The FHWA Memorandum “ACTION:  Identifying Acceptable Highway Safety Features” of July 25, 1997, provides  further guidance on crash testing requirements.
**Product description**
  The  GMS-TB Guardrail System is a Thrie-Beam longitudinal barrier which uses 12-gage 
  Thrie-Beams  mounted directly on conventional W6 x 8.5 posts without blockouts or backup  plates at any of the posts. The  Thrie-Beams are attached to the posts with a single proprietary Mini Spacer  (GMS) fastener at each post, with the fastener being attached to the Thrie-Beam  at the lower flange of the Thrie-Beam (using a 0.64 m (25 in.) mounting  height). All guardrail splices are  located at posts. The guardrail panels are  each 3.81 m (12.5 ft) long, the posts are spaced at 1.91 m (6.25 ft), and the  height of the top of the guardrail is 0.99 m (39 in). This height constitutes an increase of  approximately 100mm (4 in) compared to the conventional SGR09  (a,b,c) Thrie-Beam systems and accounts for higher centers of gravity of the current  vehicle fleet. The ground clearance of  the system is 483 mm (19 in), which is the same ground clearance that was used  in the W-beam GMS designs previously accepted by the FHWA (acceptance letter  HSA-10/B150). The proprietary GMS  fastener is a critical element of the system.  It ensures that Thrie-Beam panels disengage from the posts on impact and  are not pulled down to the ground and rotated by the posts. Such performance lowers the probability of  vehicles overriding the system. Also,  posts disengaged from the guardrail have less of a snagging potential compared  to posts attached to the guardrail. Design  details for the proprietary GMS fastener are shown in Enclosure 1.
**Test article installation**
  The  test article’s length-of-need section was 45.72 m (150 ft) long. The 12 guardrail panels between the end  anchors were each 3.81 m (12.5 ft) long, the posts were spaced at 1.91 m 
  (6.25  ft), and the height of the top of the guardrail was 0.99 m (39 in). The barrier system was terminated at either  end with modified Type T Anchors (Foundation Tube Option), without blockouts,  and without struts between posts. This  end anchor is designed to span three posts. However, rectangular washers were  added at posts 1 through 4 and 28 through 31 for purposes of this  length-of-need test only. Drawings of  the test article are presented in Enclosure 1. Note that the end anchor systems were  assembled as shown, except that Thrie-Beam rails were used in place of the  W-Beam rails and the anchor cable bracket was attached to the lower flange of  the Thrie-Beam rail.
Including  the extended end anchors, the entire longitudinal barrier spanned 31 posts,  with the length-of-need section mounted from post 4 through post 28. The total length of the longitudinal barrier  in the test installation, including the end anchors, was 57.15 m (187.5 ft).
**Testing**
  Full-scale  crash testing to evaluate the impact performance of the GMS-TB Guardrail System included test 3-11. The results of this test are summarized in  Enclosure 2. A comparison of the test  results with the evaluation criteria set forth in the NCHRP Report 350  indicates compliance with all recommended criteria for the test performed.
The GMS-TB Guardrail System performed as intended. In the posts that were directly contacted by  the test vehicle (Posts 13 through 19), the guardrail was released from the  posts. In the vehicle contact region,  all of the fasteners were sheared at the front face of the post during the  impact of the vehicle with the guardrail and posts, except for Post 16 where  the fastener was not sheared. All of  these fasteners exhibited a uniform U-shaped deformation of the release  washers. Outside of the vehicle contact  region, the fasteners in Posts 20 through 24 released from the guardrail  without being sheared, and in Post 25 the fastener released from the guardrail  and was sheared at the front face of the post. These fasteners also exhibited a uniform  U-shaped deformation of the release washers. None of the Thrie-Beams failed and all of the  splice joints remained fastened together. The guardrail was not smashed flat at any of  the posts in the impact region and for the most part maintained its Thrie-Beam  shape.
Previously,  you successfully conducted test 3-10 on a Double-Sided (median) GMS W-beam barrier (FHWA  acceptance letter HSA-10/B-150). I agree that this previously conducted test is  comparable to test 3-10 on either Single-Sided or  Double Sided GMS-TB Guardrail Systems. It  is critical that the ground clearance and mounting height of the GMS-TB  Guardrail Systems are 
  the same as those used in the 3-10 test conducted on the  GMS W-beam design accepted by the FHWA. Therefore,  I agree that test 3-10 on Single-Sided or Double  Sided GMS-TB Guardrail Systems can  be waived.
Further, test 3-11 on Double Sided GMS-TB Guardrail Systems  would be less severe than 
  test 3-11 conducted on Single-Sided GMS-TB Guardrail  System. Therefore, I agree that test  3-11 on Double Sided GMS-TB Guardrail Systems can be waived.
In  summary, I agree that both Single-Sided and Double  Sided GMS-TB Guardrail Systems, as described above, meet the appropriate  evaluation criteria for NCHRP 350 TL-3 devices and may be used at all  appropriate locations on the National Highway System (NHS) when selected by the  contracting authority, subject to the provisions of Title 23, Code of Federal  Regulations, Section 635.411, as they pertain to proprietary products.
**Standard provisions**
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 they 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-156,  shall not be reproduced except in full. As  this letter and the documentation which support it become public information,  it will be available for inspection at our office by interested parties.
  The GMS-TB Guardrail  System is a patented product and is considered "proprietary". The use  of proprietary devices specified on Federal-aid projects, except exempt,  non-NHS projects must be: (a) supplied through competitive bidding with equally  suitable unpatented items; (b) certified by the highway agency as essential for  synchronization with existing highway facilities, or that no equally suitable  alternative exists; or (c) 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.Sincerely yours,
			Signature of John R. Baxter
			John R. Baxter, P.E.
				Director, Office of Safety Design
				Office of Safety2 Enclosures
FHWA:HSSD:NArtimovich:tb:x61331:3/14/07
File: s://directory folder/nartimovich/B156-OchoaGMS-TBfin.doc
cc: HSSD (Reader, HSA; Chron File, HSSD;  N.Artimovich, HSSD; MMcDonough, HSSD)
Gregoy Mini Spacer
Figure A.1 - Gregory Industries Single-Face GMS-TB Guardrail System
Type T Anchor Assembly - Type 5 Guardrail (Detail A, Detail B, Soul Plate Detail)
Type T Anchor Assembly - Type 5 Guardrail (Elevation - Concrete Footer, Driveway Opening
Summary of Test Results and Conditions U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

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