July 16, 2004
In Reply Refer to: HSA-10/CC-69D
Mr. Kaddo Kothmann
Road Systems, Incorporated
3616 Howard County Airport Road
Big Spring, Texas 79720
Dear Mr. Kothmann:
In your May 19 letter, you requested acceptance of a modified version of your Box-Beam Burster Energy Absorbing Terminal Single-Sided Crash Cushion (BEAT-SSCC) as an National Cooperative Highway Research Program (NCHRP) Report 350 crash cushion at test level 3
(TL-3). This modified design, called the BEAT-SS-CM, consisted solely of a new breakaway post design, with the posts bolted to steel brackets mounted on either a 150-mm (6-inch) thick, reinforced concrete pad or a 200-mm (8-inch) thick non-reinforced pad, rather than set in soil. The brackets were formed from 13-mm (1/2-inch) thick steel plate and were bolted to the concrete with 19-mm diameter x 152-mm long Power Fasteners Wedge-Bolt anchors. The general layout of the BEAT-SSCC-CM is shown in the enclosure to this letter. To support your request, you submitted a copy of the Midwest Roadside Safety Facility's January 27 test report entitled "Performance Evaluation of the Concrete Mounted Single-Sided Crash Cushion - NCHRP 350 Test 3-38" and a videotape of the crash test that was conducted as well as drawings and photographs of the BEAT-SSCC-CM.
As noted in your letter, as many as seven tests (test numbers 3-30 through 3-35, and 3-39) are normally required to certify the crashworthiness of a gating terminal or crash cushion. Based on earlier tests conducted on the Wyoming DOT's box-beam terminal (WYBET), the BEAT/BEAT-MT box beam terminals, and the BEAT-SSCC and on the similarities of these designs to the BEAT-SSCC-CM, you concluded that tests 3-30, 3-31, 3-32, 3-33, 3-34, and 3-35 were not needed. My staff reviewed the information you provided and concurred with your analysis. Test 3-38, which is identified in the NCHRP Report 350 as being needed for a nongating device, was conducted to verify the lateral redirection capability of the concrete-mounted posts. In this test, the 2000-kg pickup truck impacted the side of the crash cushion
3.42 m downstream from the impact head, near post 3, at 102.1 km/h and at a 20.6-degree angle. Four posts were displaced in the test, but only two separated from the box-beam rail element. Dynamic deflection was reported to be 189 mm.
For the original ground-mounted design, test 3-38 was run twice, with one impact point at the beginning of the length of need (approximately 400 mm upstream from post 3) and the second 2.0 m upstream from the rigid New Jersey barrier. In the first test with soil-mounted posts, seven posts were displaced and failed at the ground line and the dynamic deflection was 750 mm.
Thus, for essentially the same test, the concrete-mounted design was shown to be a much stiffer system and a second test closer to the downstream concrete attachment can be presumed acceptable. However, since the front wheel of the pickup truck was torn from the vehicle in the earlier test of the BEAT-SSCC in test 3-38 when the impact point was only 2.0 m from the concrete barrier, both designs could be improved by the addition of a tapered curb that effectively blocks out the leading edge of the concrete barrier and reduces the likelihood of a wheel folding under the box-beam rail element and snagging on the concrete. A box-beam rubrail would serve the same function.
Based on the results of this test, the BEAT-SSCC-CM, as described above, may be considered an NCHRP Report 350 crash cushion at TL-3. Consequently, it may be used on the National Highway System (NHS) when such use is acceptable to the contracting authority. As with the BEAT-SSCC, the concrete-mounted design is not appropriate for use at locations where backside hits towards the rigid concrete barrier are possible, e.g., in gore areas, nor is it appropriate for use at emergency vehicle openings in an otherwise continuous run of median barrier where backside, opposite direction hits are possible. Since it is a proprietary product, its use on Federal-aid projects, except exempt non-NHS projects, remains subject to the provisions in Title 23, Code of Federal Regulations, Section 635.411.
Please note also the following standard provisions that apply to FHWA letters of acceptance:
/Original Signed by Richard Powers/
John R. Baxter,
Director, Office of Safety Design
Office of Safety
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