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U.S. Department of Transportation

Federal Highway Administration

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

November 17, 2005

In Reply Refer To:HSA-10/B-134a

Mr. Barry D. Stephens, P.E.
Sr. Vice President Engineering
Energy Absorption Systems, Incorporated
3617 Cincinnati Avenue
Rocklin, California 95765

Dear Mr. Stephens:

In my February 14 acceptance letter (HSA-10/B-134) for the Vulcan Barrier, I noted that additional information would be needed before the Vulcan could be deemed crashworthy and acceptable for use in bidirectional applications when connected to a rigid crash cushion or concrete barrier. Staff members had expressed concern about potential pocketing and/or snagging of vehicles impacting the freestanding Vulcan units immediately downstream from a rigid connection point.

In late September, you provided members of my staff data from a reverse direction crash test you ran to address the above concern. The tested transition was designed to connect freestanding Vulcan Barrier units to an anchored QuadGuard CZ. The test results for the National Cooperative Highway Research Program (NCHRP) Report 350, Test 3-21 were supplied with your transmittal in the form of a crash test video, a 1-page test summary (Enclosure 1), and before/after photographs. The transition design consisted of a galvanized steel weldment measuring 2.03-m long, 0.8-m high and a variable width that matches the Vulcan Barrier shape to a .61-m wide QuadGuard CZ System (Enclosure 2). The transition incorporates a lower steel mounting plate measuring 9.5-mm thick x 1.07-m wide x 1.22-m long with twelve (12) mounting holes for anchoring the transition to a rigid foundation. For this crash test, four (4) unanchored Vulcan segments were pinned together and the upstream end was pinned to an anchored QuadGuard backup to provide tension to the unanchored Vulcan segments. The downstream end of the unanchored Vulcan was attached to the new transition that was, in turn, attached to a 6-bay, .61-m wide QuadGuard CZ backup. The targeted impact point was the connection between the unanchored Vulcan segment and the new transition. The 2000P vehicle was contained and redirected and the reported occupant risk values were considered acceptable. However, there remained some concern that field installations would be far longer than the test installation, resulting in greater barrier deflection and consequently, more pocketing in the transition area.

To mitigate our concern about pocketing, you submitted with your November 8 letter, a modified Vulcan design that incorporates additional anchoring on the impact side of the three Vulcan sections immediately upstream from the transition (Enclosure 3). Your design gradually increases the number of anchors per section on the approach to the transition. This increase in anchors provides gradual stiffening similar to that which has been successfully tested with precast concrete barrier segments connected to a rigid concrete bridge railing.

Based upon the submitted test results and your Vulcan anchoring improvement, I agree that the proposed transition between Vulcan Barrier and anchored QuadGuard CZ Systems meets the NCHRP Report 350 TL-3 evaluation criteria and may be used on the National Highway System as a transition between these devices in bidirectional applications. I also agree that the results of the submitted test and the addition of anchors to the Vulcan units adjacent to the barrier support the acceptance of your transition between Vulcan and Concrete Median Barrier (CMB) when the Vulcan-to-CMB transition piece (Enclosure 4) is used.

Please note also that the standard provisions for the Federal Highway Administration letters of acceptance noted on my original Vulcan acceptance letter remain applicable to this transition design.


Sincerely yours,

(original signed by George Ed. Rice, Jr. for)
John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety

4 Enclosures

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