1200 New Jersey Ave., SE

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.” 

Requirements

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. 

Decision

The following device was found acceptable for use:

• Test Level 2 Scorpion Trailer Attenuator
2

Description

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. 

Findings

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:
3

• This acceptance is limited to the crashworthiness characteristics of the devices and does not 

cover their structural features, nor conformity with the Manual on Uniform Traffic Control 

Devices.

• Any changes that may adversely influence the crashworthiness of the device will require a 

new acceptance letter.

• Should the FHWA discover that the qualification testing was flawed, that in-service 

performance reveals unacceptable safety problems, or that the device being marketed is 

significantly different from the version that was crash tested, we reserve the right to modify 

or revoke our acceptance.

• You will be expected to supply potential users with sufficient information on design and 

installation requirements to ensure proper performance.

• You will be expected to certify to potential users that the hardware furnished has essentially 

the same chemistry, mechanical properties, and geometry as that submitted for acceptance, 

and that it will meet the crashworthiness requirements of the FHWA and the NCHRP

Report 350.

• To prevent misunderstanding by others, this letter of acceptance is designated as number 

CC-65G and shall not be reproduced except in full. This letter and the test documentation 

upon which it is based are public information. All such letters and documentation may be 

reviewed at our office upon request. 

• The Scorpion Trailer Attenuators are patented products and considered proprietary. If 

proprietary devices are specified by a highway agency for use on Federal-aid projects, except 

exempt, non-NHS projects, (a) they must be supplied through competitive bidding with 

equally suitable unpatented items; (b) the highway agency must certify that they are essential 

for synchronization with the 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.

• This acceptance letter shall not be construed as authorization or consent by the FHWA to use, 

manufacture, or sell any patented device for which the applicant is not the patent holder. The 

acceptance letter is limited to the crashworthiness characteristics of the candidate device, and 

the FHWA is neither prepared nor required to become involved in issues concerning patent 

law. Patent issues, if any, are to be resolved by the applicant.

Sincerely,

Michael S. Griffith

Director, Office of Safety Technologies

Office of Safety

Enclosures