Federal Highway Administration
400 Seventh St., S.W.
Washington, D.C. 20590
March 11, 2005
In Reply Refer To: HSA-10/CC-78B
Mr. Barry D. Stephens, P.E.
Senior Vice President Engineering
Energy Absorption Systems, Inc.
3617 Cincinnati Avenue
Rocklin, California 95678
Dear Mr. Stephens:
Mr. Douglas Bernard recently delivered your February 24, 2005, letter to Mr. Richard Powers of my staff. In this letter, you requested formal Federal Highway Administration (FHWA) review and acknowledgement of a successful Test Level 2 (TL-2) crash into a Safe Stop™ 180 TMA when in its folded (transport) position on a support vehicle. Your letter included a one-page test summary prepared by E-Tech Testing Services and a video of this crash event.
The tested Safe Stop 180 TMA was identical to the original design previously submitted to our office for acceptance as a test level 3 (TL-3) TMA (reference FHWA acceptance letters HSA-10/CC-78 & CC-78A). For the new test, the Safe Stop 180 was mounted to the back of an 8550-kg support vehicle and was impacted in its folded position, with the rear portion of the unit rotated onto the top of the front portion. In this configuration the top of the unit is 2.03 m (6'-8”) off the ground and it projects out from the back of its support truck 2.4 m (7'-10”).
The folded TMA was impacted head-on at 72.4 km/h by a 2026-kg pickup truck. The results of test 2-51 are summarized on the enclosed one-page test summary sheet. All reported occupant risk, vehicle trajectory and structural adequacy values were within acceptable limits. The roll-ahead distance for the support vehicle was reported to be 5.8 m.
Based upon this information, the FHWA acknowledges that the Safe Stop 180 TMA affords an acceptable level of protection in the folded position for a vehicle weighing approximately 2000 kg when impacted at speeds up to 70 km/h. In its deployed position, the Safe Stop 180 remains a TL-3 device.
Please note that this acknowledgement is for the test described above only and is not meant to imply that the folded Safe Stop 180 meets all the requirements for a National Cooperative Highway Research Program Report 350 TL-2 attenuator.
/original signed by/
John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety