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
November 3, 2010
In Reply Refer To: HSSD/CC-109
Mr. Gerrit A. Dyke, P.E.
Barrier Systems, Inc.
3333 Vaca Valley Parkway, Suite 800
Vacaville, CA 95688
Dear Mr. Dyke:
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: | X-TENuator (X-TEN); and, X-TENuator (X-TEN) with Slider Panel Modification |
---|---|
Type of system: | Redirective Non-Gating Crash Cushion |
Test Level: | TL-3 |
Testing conducted by: | Safe Technologies Inc. |
Task Force 13 Designator: | SCI23 |
Date of request: | February 25, 2010 |
Request Initially acknowledged: | March 16, 2010 |
Date of Modification received: | July 28, 2010 (letter dated July 23, 2010) |
Date of completed Modification received: | October 5, 2010 |
You requested that we find this system acceptable for use on the NHS under the provisions of the 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 or the American Association of State Highway and Transportation Officials’ Manual for Assessing Safety Hardware (MASH). The FHWA Memorandum “Identifying Acceptable Highway Safety Features” of July 25, 1997 provides further guidance on crash testing requirements of longitudinal barriers.
Description
The X-TEN system is a redirective, non-gating crash cushion. The system is designed to safely decelerate an errant vehicle to a safe stop or redirect an errant vehicle away from roadside or median hazards. Enclosure 1 shows assembly of the X-TEN system. Enclosures 2 through 18 illustrate the details of each element used in the system. The system is comprised of an energy absorbing nose cover, an energy absorbing nose cartridge, dual impact heads and cables, front cable anchors, W-Beam side panels, specially designed posts (Enclosure 8), and an independent backstop. Standard W-Beam block-out spacers (Enclosure 15) attach the side panels to the posts. The block-out spacers are tethered to the posts by wire ropes.
The system is designed to absorb the kinetic energy of the impacting vehicle. When a vehicle hits the system head-on, first energy is absorbed by the nose cover and the nose cartridge (Enclosure 13 and Enclosure 14). As the impact head is pushed back two cables (Enclosure 2) pull through a brake mechanism, dissipating energy. The depth of penetration of a vehicle into the system is dependent upon both the original impact speed and the mass of the impacting vehicle. When hit at an angle along the side beyond the first post, the system is restrained laterally by the W-Beam panels (Enclosure 6 and Enclosure 7) and cables that run the length of the system inside the panels. The front ends of the cables are attached to plates (Enclosure 12 and Enclosure 17) that are bolted to the foundation and the rear ends of the cables terminate in the backstop (Enclosure 4 and Enclosure 5) assembly.
The effective length of X-TEN system is 7.5 m (24 ft. 9 in.) and the effective overall height is 0.792 m (31.19 in.). The width of the system is 0.926 m (36.44 in.).
In addition, the following modifications and subsequent testing as submitted July 23, 2010 are as follows:
Crash Testing
The X-TEN crash cushion system was successfully crash tested as per NCHRP Report 350 test designations 3-31 through 3-33 and 3-36 through 3-39 by Safe Technologies Inc. In tests 3-31, 3-37, 3-38, and 3-39, the X-TEN system was attached to an Asphalt Concrete (AC) pad set over dense graded aggregate with forty two (42) 20 mm (3/4 inch) all thread studs embedded 400 mm (16 in.) and epoxied in place (Enclosure 19). In test 3-32, test 3-33, and test 3-36, the X-TEN system was attached to a Portland Cement Concrete (PCC) pad with twenty-six (26) 20 mm (3/4 in.) all thread studs embedded 150 mm (6 inch) and epoxied in place (Enclosure 20). Enclosures 21 through 23 summarize the results of test 3-31 through 3-33 respectively and Enclosures 24 through 27 summarize the results of test 3-36 through 3-39.
In addition, the X-TEN with slider panel modification crash cushion submission dated July 23, 2010 proposed the following:
Findings
As stated in your letter dated February 25, 2010, in accordance with NCHRP 350 tests 3-30 through 3-33 and tests 3-36 through 3-39 are to be conducted for test level 3 non-gating crash cushions approval. The system was crash tested under all of these required tests, except for test 3-30. The system described above and shown in Enclosure 1 passed all tests that were conducted. Occupant Impact Velocities (OIV) associated with all tests are below the “preferred” limit and Occupant Ridedown Acceleration (ORA) for all tests except test 3-31 are below the “preferred” limit. The ORA for test 3-31 was calculated 20 G which is the maximum allowable limit according to NCHRP 350.
In addition, you have requested test 3-30 be waived. Your request is accepted on the grounds that test 3-32 is historically more critical than test 3-30. In your letter, you have also requested FHWA acceptance of the following for the X-TEN system:
The above additional requests are also accepted. Based on the provided videos of the crash tests conducted on the X-TEN attached to AC roadways or PCC foundations, none of the bolts were pulled out. In these tests either posts collapsed or the bolts sheared. Consequently, we concur that the X-TEN system can be attached to both AC roadways and PCC foundations.
In the crash test videos associated with tests 3-31, 3-32, and 3-33 (in which the test vehicle hits the test article head-on) the test articles confirm that the vehicle is captured when impacting the first post (does not gate through) and confirms the redirective capacity beginning at the impact head behind the nose cover.
Your last request in regards to attaching to other roadside barriers is also accepted on the grounds that attaching the X-TEN system using an appropriate standard connection will not likely degrade the performance of the system.
As requested in your letter dated July 23, 2010, referencing the X-TEN with modified slider plate crash cushion, we concur that modifications (a.) through (e.) inclusive will not adversely degrade the successful crash test performance of the system and are acceptable for use on the NHS system.
In addition and in reference to modification (f.), we concur with your request for equivalence in that a bolted slider plate (vs. original welded detail) does not adversely effect the successful crash test performance of the system and is acceptable for use on the NHS system.
Also, the results of the NCHRP Report 350 Test 3-31 as conducted on the X-TEN with slider panel modification crash cushion was found to successfully meet all Test 3-31 testing criteria. A summary of the crash test is attached.
Therefore, the system described in the requests 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.
Please note the following standard provisions that apply to FHWA letters of acceptance:
Sincerely yours, /* Signature of Michael S. Griffith */
|