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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter B-196

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U.S. Department of Transportation
Federal Highway Administration

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

September 9, 2009

In Reply Refer To: HSSD/B-196

Mr. Geoff Maus
Chief Design Engineer
TrafFix Devices, Inc.
160 Avenida La Pata
San Clemente, CA 92673

Dear Mr. Maus:

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, Inc., Sentry Water-Cable Barrier
Type of system: Water filled barrier
Test Level: NCHRP Report 350 TL-1, TL-2 and TL-3
Testing conducted by: Karco Engineering, LLC
Date of request: January 21, 2009
Date of completed package: July 27, 2009
Request initially acknowledged: January 26, 2009

You requested that we find this system acceptable for use on 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 systems should meet the guidelines contained in the NCHRP Report 350. The FHWA Memorandum “ACTION: Identifying Acceptable Highway Safety Features” of July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers.

Description
The TrafFix Devices, Inc., Sentry Water-Cable Barrier was designed without the need for an external attached structure to meet Test Level 2 (TL-2) and TL-3 barrier performance. A second design objective was to produce a product with minimal lateral deflection of the barrier. Each section is a freestanding longitudinal wall unit with an approximate width, height, and length of 25 inches by 46 inches by 84 inches (635 mm x 1092 mm x 2032 mm) respectively.

Each section has 11 connecting lugs, 5 on one end, and 6 on the opposite end. The four upper lugs on each barrier section contain one each independent corrosion resistant steel wire rope molded into the Sentry Water-Cable Barrier. The four wire rope pieces in each section act similarly to a cable barrier when impacted. A 1.25-inch (31.8-mm) diameter steel T-pin drops through the 1.5-inch (38.1-mm) diameter holes in the lugs, linking the sections together. The shell of each section is made up of high density polyethylene (HDPE).

Water-Cable Barrier wall sections are set in position, connected by the T-pin and T-pin clip, and filled with water. The empty weight of each Water-Cable Barrier section is approximately 165 pounds (75 kg). The weight of each Water-Cable Barrier section when filled with water is approximately 2,150 pounds (975 kg). The TrafFix Devices, Inc., Sentry Water-Cable Barrier does not use an external structure to achieve TL-2 or TL3 barrier performance, reducing the chance of improper assembly of the barrier.

Crash Testing
Three full scale crash tests were performed on a series of 25 linked Water Wall sections. The Water Wall sections were filled with water; no sections were anchored to the ground. The impact point was the center of the thirteenth barrier section from the beginning of the series. The 25 linked Sentry Water-Cable Barrier sections provided a tested length of approximately 158 feet (48 m). The Water-Cable Barrier system length and impact point were chosen to replicate previous tests performed on products of this category. The impact point at the center of the Water-Cable Barrier was also deemed to be “worst case”, as it is the mid point between the supported ends. The test data summary sheets for the three tests, NCHRP Report 350 Test 2-11, 3-10, and 3-11 are enclosed for reference. In each case the vehicle was captured by the barrier system with the vehicle experiencing substantial pitching and yawing. However, the vehicle remained upright in contact with the barrier and did not rebound into adjacent lanes. All occupant risk values were within allowable limits. The design deflection distance, as recorded in Test 3-11, was 9 feet (2.74 m).

Findings
You requested the following FHWA Acceptance conditions for the Sentry Water-Cable Barrier:

Request #1: Longitudinal Barrier at Test Levels TL-3, TL-2, and TL-1

Request #2: Longitudinal Channelizing Device at Test Levels TL-3, TL-2 and TL-1.

We concur that the system described above and detailed in the enclosed drawings is acceptable for use on the NHS above as a barrier and a longitudinal channelizing device under the range of conditions tested and as expanded in Requests #1 and #2, when such use is acceptable to a highway agency. TL-1 performance is assumed based on the successful TL-2 and TL-3 testing.

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

 

Sincerely yours,

Signature of David A. Nicol

David A. Nicol, P.E.
Director, Office of Safety Design
Office of Safety

Enclosures

Page last modified on June 24, 2011.
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