U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000
U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Ave. S.E.
Washington, D.C. 20590
March 15, 2010
In Reply Refer to: HSSD/CC-12Q
Mr. Steve Brown
President
Trinity Highway Products, LLC
2525 N. Stemmons Freeway
Dallas, TX 75207
Dear Mr. Brown:
This letter is in response to your request for the Federal Highway Administration (FHWA) acceptance of roadside safety devices for use on the National Highway System (NHS).
You requested that we find these devices 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.”
Requirements
Roadside safety devices should meet the guidelines contained in the NCHRP Report 350 FHWA Memorandum “Action: Identifying Acceptable Highway Safety Features” of July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers.
Description
The ET-Plus and ET-Plus 31 have been successfully crash tested and accepted by the FHWA, most recently in FHWA Acceptance CC-12J, dated June 24, 2002, CC-12L, dated April 11, 2003, and CC-94, dated September 2, 2005. The use of one anchor post and subsequent transition to standard line posts were the same in these two w-beam guardrail terminals. The obvious difference is the use of seven additional breakaway posts and the 27 5/8-inch rail height in the ET-Plus and five additional breakaway posts and 31-inch rail height in the ET-Plus 31. Recent full scale crash tests have demonstrated that an 820C vehicle can safely ride down full strength W6x8.5 steel line posts that are not rigidly connected to the w-beam rail. Your present request is to replace the last six breakaway posts in ET-Plus and the last 4 breakaway posts in the ET-31with these standard W6x8.5 line posts.
Crash Testing
In the safety performance evaluation of these new designs, full-scale crash tests were not conducted on either revised design. NCHRP recommends a total of up to 7 full-scale crash tests for gating guardrail terminals. We concur that none of these tests is needed to verify the safety performance of the proposed new terminal designs, as summarized below.
Test 3-30 involves an 820C vehicle striking the end of the terminal at a speed of 100 km/hr with ¼ offset and an angle of 0°. Recent full scale crash tests have demonstrated that an 820C vehicle can safely ride down full strength W6x8.5 steel line posts. Hence, Test 3-31 is not necessary for evaluating the performance of the new terminal designs.
Test 3-31 involves a 2000P vehicle striking the end of the terminal at 100 km/h and 0°. Numerous full-scale crash tests have shown that the 2000P vehicle is capable of riding down full strength guardrail posts. Further, the previous results of test 3-30 provide a much better indication of the consequences of a vehicle striking an unmodified line post. Thus, Test 3-31 is not necessary for evaluating the performance of the new terminal designs.
Test 3-32 requires an 820C vehicle striking the end of the terminal at 100 km/h and an angle of 15°. Historically the third post in a tangent energy absorbing terminal has not been broken during this impact. Nothing was changed upstream of post #3 from the systems that were approved previously. Therefore, we concur there is no need to conduct this test.
Test 3-33 incorporates the same impact conditions as test 3-32 with a 2000P vehicle. This test is not necessary for the same reasons that Test 3-32 is not required.
Test 3-34 involves an 820C vehicle striking the terminal at its critical impact point at a speed of 100 km/h and an angle of 15°. Previous 3-34 testing was successfully conducted on ET-Plus (HSA-10/CC-12J) with W8x10 breakaway Steel Yielding Terminal Posts (SYTP)] at post locations 2 through 8. Also, this test was successfully conducted with another terminal at a greater impact angle than would be required with the ET-Plus and ET-31. Therefore, we concur there is no need to conduct this test.
Test 3-35 examines the safety performance of the terminal for impacts at the beginning of the length-of-need. This test involves a 2000P striking at the beginning of length-of-need. Previous 3-35 testing was successfully conducted on ET-Plus and ET-Plus 31 with breakaway posts (SYTP) at post locations 2 through 8 and 2 through 6 respectively. Therefore, 3-35 testing on the terminals with full strength W6x8.5 steel line posts at post location 3 and beyond is not required.
Test 3-39 involves a 2000P vehicle impacting the midpoint of the terminal in a reverse direction at a speed of 100 km/h and an angle of 20°. As mentioned above the 2000P test vehicle has been shown to be capable of riding down a full strength line post without posing serious threats to the occupants. Hence this test is also considered to be unnecessary.
In these tests we concur that the performance of the last six breakaway posts in the ET-Plus and the last 4 breakaway posts in the ET-31 terminals would not have been adversely affected by replacing the yielding posts with standard line posts.
Findings
The modified ET-Plus and ET-Plus 31 described above and detailed in the enclosed drawings are acceptable for use on the NHS under the range of conditions tested, when acceptable to a highway agency.
Please note the following standard provisions that apply to FHWA letters of acceptance:
This acceptance is limited to the crashworthiness characteristics of the devices 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 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, 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 CC-12Q 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 ET-Plus and ET-Plus 31 end terminals are patented products and considered proprietary. If 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 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,
David A. Nicol, P.E. |
