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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter CC-47D

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U.S. Department of Transportation
Federal Highway Administration

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

February 13, 2009

In Reply Refer To: HSSD/CC-47D

Mr. Barry D. Stephens, P.E.
Sr. Vice President Engineering
Energy Absorption Systems, Inc.
3617 Cincinnati Avenue
Rocklin, CA 95678

Dear Mr. Stephens:

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 system: Mod. TRITON Concrete End Treatment ACZ-350™ System
Type of system: Non-redirecting barrier terminal
Test Level: NCHRP Report 350 TL-3
Testing conducted by: E-Tech Testing Services, Inc.
Date of request: December 17, 2008

You requested that we find this system acceptable for use on the NHS under the provisions of 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 “Identifying Acceptable Highway Safety Features” of July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers.

Description
The ACZ-350TM System is designed to perform as a narrow, non-redirecting crash cushion to shield the blunt ends of both permanent and variable length portable concrete median barrier (P/CMB), as well as crashworthy steel median barrier systems such as the Vulcan Barrier.

The ACZ-350TM System consists of a sheet metal nose, four water-filled plastic shell segments, and a steel transition pinned together to act as an end treatment. The nose is constructed of light gauge steel and connects directly to the front-most water filled segment. Each of the four water filled segments is equipped with an external, top-mounted steel stiffener which is rigidly fixed to each respective segment. The front two water filled segments do not contain an internal steel frame or external, side-mounted laminated steel straps. In contrast, the next (or last) two water filled Triton segments are equipped with an internal steel frame as well as external side-mounted steel laminated straps. A heavy duty non-crushable steel transition completes the system by connecting the last water filled segment to the blunt end of the downstream barrier, be it P/CMB or Vulcan barrier. The total length of the ACZ-350TM System is 9.6 meters (31’-7”). In bi-directional traffic applications, there are no rigid exposed vehicle snag points for traffic traveling from the reverse direction.

Crash Testing
You requested acceptance of the ACZ-350TM System based on the successful results of three NCHRP Report 350 crash tests. The first was Test 3-40 in which an 820C compact car impacted the unit head-on, and with the vehicle offset at w/4. The second test was Test 3-41 in which a 2000P pickup truck impacted the unit head-on. The third test was a modification of Test 3-44 in which a 2000P vehicle impacts the side of the system at 20 degrees with the centerline of the vehicle aligned with the centerline of the rigid hazard. The NCHRP Report 350 states that the intent of Test 3-44 is “…to evaluate the ability of the cushion to safely stop a large passenger car prior to a life-threatening impact with the corner of the hazard object being shielded.” Aligning the centerline of the impacting vehicle at the center of the shielded concrete barrier is clearly the critical impact point for the ACZ-350 design and the impact conditions are essentially the same as Test 3-38 for redirecting crash cushions. Report 350 acknowledges that test 3-38 “would be difficult to pass for a nonredirective crash cushion”, and thus does not require that the nominal limiting occupant impact velocities and ridedown accelerations be achieved. However, we recognize your newly designed ACZ-350TM System is a nonredirective crash cushion that meets the occupant impact velocities and ridedown accelerations with reported values of 10.5 m/s and 18.4 g’s while the impacting vehicle showed no evidence of penetration, climbing or vaulting.

We agree with your conclusions that Tests 3-42 and 3-43 do not require retesting. There has been no significant change in system shape, system height or component weights between the original TRITON CET and the ACZ-350. Individual system sections near the front of the system are designed to articulate in the same fashion as the TRITON Concrete End Treatment. This articulation will allow the errant vehicle to pass through the system as expected for a gating system. Based on these design principals we believe the new ACZ-350TM system will behave with similar results as the TRITON Concrete End Treatment when tested to 3-42 and 3-43 criteria.

Findings
Based upon the results of the reported Tests 3-40, 3-41, and 3-44, and the discussions above, the FHWA concludes the ACZ-350TM System is acceptable for use on the NHS to act as a narrow, non-redirecting gating crash cushion for permanent and portable concrete median barrier of varying individual lengths as well as steel barrier such as Vulcan. It is acceptable for use on the NHS under the range of conditions tested, when such use is acceptable to a highway agency. The cushion should be used in locations where side impacts are unlikely, penetration behind the barrier is acceptable for angled nose impacts, and where the use of a redirective crash cushion is not feasible for reasons other than cost or convenience.

Please note the following standard provisions that apply to the 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 January 17, 2013.
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