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Safety Eligibility Letter CC-108

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U.S. Department of Transportation
Federal Highway Administration

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

November 10, 2010

In Reply Refer To: HSSD/CC-108

Mr. Felipe Almanza
TrafFix Devices
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 system for use on the National Highway System (NHS).

Name of system: TrafFix Devices Sentry End Treatment
Type of system: Crash Cushion
Test Level: NCHRP Report 350 TL-2
Testing conducted by: KARCO Engineering
Task Force 13 Designator: Pending
Date of request: November 11, 2009
Date of completed package: April 29, 2010
Request initially acknowledged: February 1, 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 TrafFix Devices test level 2 (TL-2) Sentry End Treatment is a terminal for the TrafFix Devices Sentry Water-Cable Barrier. The Sentry End Treatment consists of three sections made of high density polyethylene (HDPE). The Sentry End Treatment sections and the Sentry Water-Cable Barrier sections are identical in shape and size. The end treatment sections are yellow in color, whereas the barrier sections are white and orange. Each end treatment section is freestanding with an approximate width, height, and length of 22-1/2 inches, 46 inches, and 84 inches respectively. Each section has 11 connecting lugs, with 5 of them on one end and six on the opposite end.

Each of the four upper lugs on each Sentry End Treatment section contains an independent corrosion resistant steel wire rope. A 1-1/8-inch diameter steel T-pin drops through the 1.5-inch diameter holes in the lugs, linking the sections together. The empty weight of each wall segment is approximately 160 pounds, prior to them being filled with water.

Upon installation, each of the end treatment sections is filled to a depth of approximately 9 inches of water ballast. The first Sentry End Treatment section will have a rounded steel end cap marked with retro-reflective materials. The second and third sections, in the area of the end treatment cavity above the water are pre-filled with energy attenuating foam.

The weight of the first section, when filled with water, is approximately 520 pounds. The second and third sections weigh approximately 550 pounds because of the additional weight of the foam.

The sections are set in position, connected by the T-pin and T-pin keeper, and filled with water to the indicated level. The second and third sections have previously had the foam installed with a pathway through the foam for filling with water. Anti-rotation spacer frames are installed on the rearward end of each consecutive Sentry End Treatment sections. Filling the space between two connecting elements eliminates the rotation between the sections. Enclosure 1 illustrates detailed design drawings and general layout of the end treatment.

Crash Testing
The Sentry End Treatment was crash tested by KARCO Engineering according to NCHRP Report 350 test designations 2 -40, 2-41, 2-43, and 2-44 guidelines. As described above, the test article consisted of three yellow sections which measured 19.3 ft. The test article was linked to 12 to 14 Sentry Water-Cable Barrier sections (orange and white) according to this chart:

Test Number Number of Sentry Sections
2-40 Fourteen
2-41 Twelve
2-43 Twelve
2-44 Twelve

The overall length of the test article ranged from 94.8 ft to 106 ft, 8-3/8 in.

In all of the tests the test vehicles remained upright. The post-impact trajectory of the test vehicles show that the vehicles did not rebound into adjacent lanes. All occupant risk values are below the preferred limits in all four tests. Enclosures 2 through 5 summarize the results of test 2-40 through 2-44 respectively.

According to NCHRP 350, test designations 2-40, 2-41, 2-42, 2-43, and 2-44 are to be conducted for non-redirective gating crash cushions for TL-2. All of these tests were conducted except test designation 2-42. The system described above and shown in Enclosure 1 passed all tests which were conducted. In your letter you requested test 2-42 be waived. Your request is accepted on the grounds that the main purpose for test 2-42 is evaluation of Occupant Impact Velocity (OIV) and Occupant Ridedown Acceleration (ORA) when a small car (820 kg) impacts the crash cushion. However, the 820C vehicle impacted the system head on (with 1/4 of vehicle width offset) and the OIV and ORA are below preferred limits. The design of the crash cushion is such that it provides more stiffness longitudinally than laterally. Consequently, it is expected that the crash cushion would have passed test 2-42 had it been conducted. The TrafFix Devices TL-2 Sentry End Treatment system is designed to be attached to a minimum of ten and without limit to the maximum number of Sentry Water Cable Barrier sections.

The system described above is acceptable for use on the NHS, 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

5 Enclosures

Page last modified on January 17, 2013.
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