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Safety Eligibility Letter CC-65G

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U.S. Department of Transportation
Federal Highway Administration

1200 New Jersey Ave. S.E.
Washington, D.C. 20590

April 21, 2011

In Reply Refer To: HSST/CC-65G

Mr. Felipe Almanza
TrafFix Devices Inc.
160 Avenida La Pata
San Clemente, CA 92673

Dear Mr. Almanza:

This letter is in response to your request for the Federal Highway Administration (FHWA) acceptance of a roadside safety device for use on the National Highway System (NHS).

Name of device: Scorpion Trailer Attenuator
Type of device: Truck Mounted Trailer Attenuator
Test Level: NCHRP Report 350 Test Level 2
Testing conducted by: Karco Engineering
Date of request: November 30, 2010
Completed package received: December 2, 2010
Request acknowledged: December 8, 2010

You requested that we find this system acceptable for use on the NHS under the provisions of the National Cooperative Highway Research Program (NCHRP) Report 350 “Recommended Procedures for the Safety Performance Evaluation of Highway Features.”

Roadside safety devices should meet the guidelines contained in the NCHRP Report 350 or the American Association of State Highway and Transportation Officials’ Manual for Assessing Safety Hardware (MASH). The FHWA memorandum “Identifying Acceptable Highway Safety Features” of July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers.

The following device was found acceptable for use:

The TrafFix Devices, Inc. Scorpion Trailer Attenuator device consists of four major components: (1) Telescopic Anti-Rotation System (TARS) tongue; (2) aluminum curved cartridge tubes; (3) attenuator boxes; and (4) axle wheel assembly. Enclosures 1 and 2 show each component of the device.

The TARS tongue attaches the device directly to a host vehicle’s pintle hook from a standard lunette eye. The TARS tongue provides a single point attachment with anti-rotation built-in. Upon impact the energy shears a steel pin allowing the tongue’s inner and outer tubes to slide forward relative to each other. Anti-Rotation supports come into contact with the support truck’s frame plate. This contact acts as a positive stop to the trailers rotation and induces a reactive force to counter the rotation, which prevents the attenuator from rotating around the back of the support vehicle.

The aluminum cartridge section is comprised of a structural energy absorbing curved aluminum tube framework. The aluminum curved cartridge tubes bolt directly to the TARS steel angles and rear axle diaphragm. Upon impact the aluminum curved cartridge tubes kink and bend, dissipating kinetic energy. Two sets (four curved tubes) of cartridge tube assemblies are used in each device.

Three crush modules are used on each device: Modules A, B, and C (Enclosure 3). Module A is the rearmost module and is typically the first module to be impacted. Modules B and C are located inside the circular curved aluminum cartridge tubes. These honeycomb shape modules are flattened from their expanded state once impacted. The modules are bolted to the TARS tongue and the rear axle diaphragm. Located at the rear of the cartridge is an axle diaphragm frame which provides a stable platform for the axle and wheel assembly.

The overall dimensions are 3.7 m (12.3 ft) long by 2.6 m (8.4 ft) wide by 0.9 m (3.0 ft) tall. It weighs approximately 677.5 kg (1490 lb) fully assembled.

Crash Testing
The Test Level 2 (TL-2) Scorpion Trailer Attenuator was conditionally accepted by FHWA in our letter CC-65D dated March 3, 2008. During the evaluation period no impacts were experienced by the TL-2 trailer, so you chose to have the unit crash tested by KARCO Engineering according to NCHRP 350 test designations 2-50 and 2-51 guidelines. All occupant impact velocities and occupant risk values were within allowable limits in both tests. The test vehicle was not penetrated during the tests. Enclosures 4 and 5 summarize the results of test 2-50 and 2-51, respectively. It should be noted that the support vehicle left side roll-ahead and right side roll-ahead distances in test 2-51 were measured at 1452 mm (57 inches) and 1489 mm (59 inches) respectively.

Tests 2-50 and 2-51 are to be conducted according to NCHRP 350 guidelines for Truck Mounted Attenuators for TL- 2 approval. The Scorpion Trailer Attenuator described above and shown in Enclosure 1 through 3 has successfully passed both tests.

Therefore, the device described in the requests above and detailed in the enclosed drawings is acceptable for use on the NHS under the range of conditions tested, when such use is acceptable to a highway agency.

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


Sincerely yours,

/* Signature of Michael S. Griffith */
Michael S. Griffith
Director, Office of Safety Technologies
Office of Safety


Page last modified on January 17, 2013.
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