January 28, 2004
Refer to: HSA-10/B-88A
Mr. Michael Kempen
46-04 245th Street
Douglaston, New York 11362
Dear Mr. Kempen:
In your September 15, 2003, letter addressed to Mr. Richard Powers of my staff, you requested formal acceptance of a tensioned 4-wire rope system (named Safence 350 4RI) as an National Cooperative Highway Research Program (NCHRP) Report 350 test level 3 (TL-3) bi-directional (median) traffic barrier. A similar 4-wire design intended for use as a roadside barrier was accepted for use on the National Highway System (NHS) in Mr. Frederick G. Wright's July 13, 2001, letter to Mr. Mats Heinevik. To support the current request, you also sent copies of test reports prepared by the VTI test laboratory in Linkoping, Sweden under the direction of Messrs. Thomas Turbell and Jan Wenall, and digitized videos of the two tests that were conducted. These tests were NCHRP Report 350 test 3-11 (Test No. 56592) with a pickup truck and CEN test TB 11 (Test No. 56379) that uses a small car and is comparable to NCHRP Report 350 test 3-10.
The Safence 350 4RI test installations were 116 meters long for test 3-11 and 71-m long for test TB 11, including anchorages. For test 3-11, the four 19-mm diameter steel cables were supported on 1900-mm long I-section steel posts driven directly into a strong soil and spaced on 2500-mm centers. These posts were made with 4-mm thick steel and had flange and web widths of 41 mm and 80 mm, respectively. For test TB 11, the posts were 1230-mm long and set into concrete cylinders 200-mm in diameter and 600-mm deep. For both installations, the posts were 780 mm above the ground. The cables were set, using spacers, into a vertical slot cut into the web of each post at heights of 720 mm, 640 mm, 560 mm, and 480 mm above the ground for test 3-11. Each cable was set 20 mm higher for test TB 11. Once in place, the cables were tensioned to the manufacturer's specifications, the exact amount depending on the ambient temperature at the time of installation. This tension can vary from just under 8 kN at 38 degrees Celsius to just over 31 kN at -40 degrees Celsius. Enclosure 1 includes a schematic drawing of the Safence 350 4RI as tested with the pickup truck as well as additional barrier layout and installation information.
For test 3-11, a 2095-kg pickup truck impacted the barrier at 97.7 km/h at 25degrees. Accelerometer data was lost in this test so occupant impact velocity and maximum ridedown accelerations were not calculated. However, these evaluation criteria have always been well below allowable limits with flexible barrier systems when smooth vehicular redirection is observed in the test as was the case for test 3-11. Dynamic deflection was 2.7 meters. For test 3-10, a Ford Fiesta impacted the wire rope at 105 km/h and an impact angle of 19 degrees. Maximum occupant impact velocity was 5.5 m/sec and maximum ridedown acceleration was reported as 6 g's. Dynamic deflection was 0.8 meters.
Based on staff review of the information you provided, I concur that the 4-strand Safence 350, as tested with either vehicle, meets all evaluation criteria for an NCHRP Report 350 roadside barrier at TL-3 and it may be used on the NHS when such use is proposed by the contracting agency. Since this product is made from steel and is proprietary, the provisions of Sections 635.410 (Buy America) and 635.411 (Use of Proprietary Products) of Title 23 Code of Federal Regulations, copies of which have been previously sent to you, are both applicable to the Safence 350 4RI design.
You have not developed a crashworthy terminal for either system. The terminal design used in the test may be used for field installations if it is located beyond the minimum clear zone or appropriately shielded.
(original signed by John R. Baxter)
John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety