December 10, 2003
Refer to: HSA-10/CC42-A
Barry D. Stephens, P.E.
Senior Vice President of Engineering
Energy Absorption Systems, Incorporated
3617 Cincinnati Avenue
Rocklin, California 95765
Dear Mr. Stephens:
In his July 16, 1997, letter to Mr. J. M. Essex, Mr. Dwight A. Horne accepted a 6-bay QuadGuard designed to shield an obstacle up to 2286-mm wide (QuadGuard-Wide) for use on the National Highway System (NHS). With an effective attenuator length of 6.7 m, this design resulted in a maximum side panel flare of 6 degrees.
Your November 15, 2003, letter to Mr. Richard Powers of my staff requested acceptance of a 6-bay QuadGuard-Wide attenuator with a side panel flare of 10 degrees designed to shield an obstacle 3.0-m wide (as shown in Enclosure 1). To support this request, you ran two tests to verify the crash performance of the wider design. Members of my staff had previously agreed that this minimum test matrix comprised the most critical tests for the wider QuadGuard and that the remaining tests could be waived. The summary results of the two successful tests (NCHRP Report 350 tests 3-32 and 3-38) are shown in Enclosures 2 and 3. To meet the Report 350 occupant risk parameters for test 3-32, a lightweight front diaphragm was designed and used in that test. This design is shown as Enclosure 4.
Based on staff review of the tests you conducted, I agree that 6-bay (or longer) QuadGuard units with a side panel flare not to exceed 10 degrees may be used on the NHS as test level 3 attenuators when the lightweight front diaphragm is used. For obstacles wider than 3.0 m, the 10-degree angle may be extended by adding increasingly wider diaphragms to the attenuator or, preferably, by continuing the same flare with a crashworthy transition connecting the back corners of the QuadGuard to the shielded obstacle.
/Original signed by/
John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety