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Home > Roadway Departure Safety > Policy/Guidance > Roadside Hardware Policy and Guidance > Barrier Terminals/Crash Cushions

 

 

400 Seventh St., S.W.
Washington, D.C. 20590

August 16, 2005

In Reply Refer To: HSA-10/CC-93

Mr. Michael Kempen, Vice President
Safence, Inc.
46-04 245th Street
Douglaston, New York 11362

Dear Mr. Kempen:

In your letter to Mr. Richard Powers of my staff that he received on July 19, you requested the Federal Highway Administration's (FHWA) acceptance of a cable barrier terminal designed for use with the Safence Cable Barrier. With your letter, you submitted copies of crash test reports prepared by the VTI laboratory in Linkoping, Sweden under the direction of Messrs. Jan Wenall and Thomas Turbell and digital videos that documented the results of the crash tests that were conducted on this terminal.

The Safence cable barrier terminal consists of a concrete end anchor in which is embedded a fabricated steel plate. The four 19-mm diameter steel cables are connected to this plate. The first I-beam anchor post, approximately 300-mm high, is set 2 m beyond the anchor and each of the next 9 posts, set on 1-m centers, increase uniformly in height until the first full-height post is reached, 12 m from the anchor point. Succeeding line posts are all 800-mm above ground level with a 430-mm embedment depth and spaced on 2.5 m centers. All posts are set in precast concrete cylinders 0.6-m deep and 0.2 m in diameter. All posts have a 20-mm wide vertical slot to hold the four cables, which are separated from each other by 80-mm high plastic spacers. These and other details are shown in Enclosure 1.

The National Cooperative Highway Research Program (NCHRP) Report 350 tests 3-30, 3-34, 3-35, and 3-39 were successfully conducted and the summary results of each are shown in Enclosure 2. My staff had previously agreed that, upon successful results of tests 3-30 and

3-34, tests 3-31, 3-32 and 3-33 could be waived for your specific terminal design. Therefore, based on the test results, the Safence Cable Barrier Terminal, as described above, may be considered an NCHRP Report 350 terminal at test level 3. The C-posts, noted in the FHWA acceptance letter B-88C as an alternative to the original I-posts used with the Safence barrier proper, may also be substituted for the I-posts in your terminal design. In test 3-35, the pickup truck impacted the terminal approximately 0.6 m downstream from the first full-height post and was contained and redirected. Thus, the beginning length of need for the Safence terminal is just beyond the first standard post, 12.6 m from the terminal anchor.

We noted that in test 3-30, the impacting vehicle attained a roll angle of nearly 50 degrees before exiting the test installation and in test 3-34, the small car over-rode the terminal and proceeded well beyond the barrier proper. These results are similar to most non-energy absorbing terminals in general and to cable barrier terminals in particular. These test results emphasize the fact that your terminal, like all cable terminals tested to date, has virtually no attenuating capability. Thus, vehicles impacting the end will normally continue a significant distance behind and beyond the barrier and are then likely to encounter non-traversable terrain or other roadside hazards or encroach into opposing traffic lanes when the barrier is used in a median. Designers must take this fact into account when selecting an optimum location for terminals in the field. It is noteworthy, however, that your terminal is not a breakaway-type design and impacts at the terminal are not likely to release tension in any of the wire ropes. Thus, the barrier proper can be expected to remain functional in most cases following such hits.

Please note also the following standard provisions that apply to the FHWA letters of acceptance:

(a) must be supplied through competitive bidding with equally suitable unpatented items; (b) the highway agency must certify that they are essential for synchronization with 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.

(Original Signed by)
John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety

2 Enclosures


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