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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter CC-119

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U.S. Department of Transportation
Federal Highway Administration

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

August 22, 2011

In Reply Refer To: HSST/CC-119

Mr. Dallas James
Armorflex International Ltd.
8 Paul Matthews Road,
North Harbour 0751
New Zealand

Dear Mr. James:

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 systems: ArmorZone™ Plastic Longitudinal Barrier; and, ArmorZoneā„¢ Plastic End Treatment
Type of system: Longitudinal Barrier and End Treatment
Test Level: NCHRP Report 350 Test Level 2 and MASH Test Level 2
Testing conducted by: Holmes Solutions Ltd (HSL) and Safe Technologies, Inc (STI).
Date of request: December 14, 2010
Request Initially acknowledged: December 17, 2010
Task Force 13 Designator: SWM17 (Barrier)
SCI29 (End treatment)

You requested that we find your 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" and the AASHTO "Manual for Assessing Safety Hardware" (MASH).

Requirements
Roadside safety devices should meet the guidelines contained in the NCHRP Report 350 when tested prior to January 1, 2011, and the American Association of State Highway and Transportation Officials'Manual for Assessing Safety Hardware (MASH) if tested after that date.  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 devices are found to be acceptable, with details provided below:

The following device was not found acceptable:

Description
ArmorZone™ is a relatively low cost longitudinal barrier designed with an integral end treatment for use in work zone applications.  The system will contain or redirect an errant vehicle when impacted beyond the beginning length of need, and is a gating design when impacted at or nearer to the upstream end terminal.  Each ArmorZone™ unit is made from High Density Polyethylene (HDPE).  It is a one piece roto-molded unit with a fill hole located on the top for internal access and a drain hole, complete with bung, at the bottom.  The original design was filled with 520 liters (137 gallons) of water.  The modified design, tested with the MASH pickup truck, contained 440 liters (116 gallons).  The unit also has a series of ‘through holes' which provide additional strength to the barrier during impact and also allow the unit to maintain its shape when filled with water.  The units tested to MASH specifications each contain a 2152-millimeter (85-inch) galvanized steel bar, 75-millimeter (3-inch) wide by 6-millimeter (½-inch) thick.  The steel bar is fitted through each unit, approximately 120-millimeters (5-inches) from the top of the barrier, and has 2 holes at either end which line up with the connection holes at each end of the HDPE unit. The ArmorZone™ unit has a nominal joined length of 2000-millimeters (79-inch), is 450-millimeters (18-inch) wide and 860-millimeters (34-inch) high.  When multiple units are connected to each other and filled with water, they form a longitudinal barrier.  They are connected with ‘twin pin'connectors, consisting of two 37-millimeter (1½-inch) diameter by 850-millimeter (33½-inch) long steel pipes complete with internal RHS reinforcement.  Enclosure 1 shows the design details for the MASH design.  The NCHRP Report 350 design is identical but does not include the steel bar.

The ArmorZone™ end treatment is similar in appearance to the barrier segments, but is not filled with water and has additional holes and slots which reduce the strength of the unit to ensure crashworthiness. It does not include the steel bar found in the MASH barrier units. Enclosure 2 shows these details.

In all ArmorZone™ installations, every unit forming the barrier (except the ArmorZone™ end treatment unit) must be filled with the correct amount of water.  Also the individual units must be connected to each other with the ‘twin pin'connector but not fixed or anchored to the ground in any way.

Crash Testing

  1. Testing Summary and Results for the ArmorZone™ longitudinal barrier:

    Test 2-10 and 2-11 were conducted by Holmes Solutions Limited in New Zealand. Both tests were run on the original all-plastic barrier design (System "A") and on 50-meter (164-foot) long installations with the impact points 13.6 meters (45 feet) from the upstream end.  Though Test 2-10 met NCHRP Report 350 evaluation criteria, in Test 2-11, the pickup truck was re-directed and came to rest on top of the barrier after very nearly going over the top.  Barrier deflection was reported to be 2.1 meters (83 inches).  Because the truck was not contained by the barrier, FHWA considers this result a failure of the NCHRP Report 350 version of the device. Enclosures 3 and 4 are summaries of both tests.
     
    Test 2-11 was re-run by Safe Technologies, Inc. using the MASH pickup truck to validate the design changes noted above (the addition of an internal steel bar and another ‘through hole’, plus reducing the water volume by 80 liters (21gallons). This test installation was also 50 meters (164 foot) long but the impact point was 23 meters (75 feet) from the upstream end.  The pickup truck was smoothly re-directed with a maximum barrier deflection of 4.1meters (13.5 feet). Enclosure 5 is the test summary sheet (System "B").

  2. Testing Summary and Results for the ArmorZone™ end treatment:

    Each of the three end treatment tests were conducted by Safe Technologies, Inc. (System "C").  Tests 2-40 and 2-41 were run on 26-meter (85-foot) long installations backed up to free-standing concrete barrier segments.  In both tests the vehicles were brought to controlled stops and the occupant risk values where within the preferred limits. However, in Test 2-40, the end treatment and adjacent barrier units slid up and across the hood of the small car, resulting in extensive windshield damage.  Enclosures 6 and 7 are summaries of these two tests.

    Test 2-43 was run on a 40.2-meter (132-foot) long installation.  The vehicle gated through the system as designed and came to rest approximately 30 meters (98 feet) downstream on the backside of the test installation.  Enclosure 8 is the test summary sheet.

    NCHPR Report 350 requires five tests for a non-redirective, gating terminal or crash cushion.  You omitted Test 2-42 from the test matrix for the end treatment because Test 2-40 is a worse case test for occupant risk for the 820C vehicle and Test 2-43 is a worse case test for vehicle trajectory with the 2000P vehicle rather than the small car.  The FHWA agrees with your reasoning for omitting Test 2-42.

    You also omitted Test 2-44 which is intended to test the crashworthiness of a non-redirective terminal used to shield a rigid object.  Because your barrier is not rigid, it is more appropriate to determine the point at which the barrier/terminal combination ceases to be gating but, instead, captures or redirects an impacting vehicle.  The FHWA agrees with your analysis that NCHRP Report 350 Test 2-11 is a good substitute for Test 2-44 since that test was run with the impact point 13.6 meters (45 feet) from the upstream end and the vehicle was redirected.  Your MASH Test 2-11was run with the impact point 23 meters (75 feet) from the upstream end of the test installation and the heavier MASH truck was also redirected.  Since the Test 2-11 impact angle is 25 degrees and the 2-44 impact angle is only 20 degrees, we agree that test 2-44 can be waived.  Based on these two barrier tests, the beginning length of need point should begin approximately 13.6 meters (45 feet) downstream from the nose of the installation for the Report 350 design and 23 meters (75 feet) downstream for the MASH design.  Should you wish to establish a length of need closer to the beginning of the barrier, additional testing will be required to determine the point at which containment or redirection can be attained.

Findings
You requested FHWA acceptance of the following two configurations for the ArmorZone™ longitudinal barrier:

  1. NCHRP Report 350 TL-2 design
  2. MASH TL-2 design.

In addition, you requested FHWA acceptance of the following configuration for the ArmorZone™
end treatment:

  1. NCHRP Report 350 TL-2 design

Systems "B" and "C" described above and shown in the Enclosures successfully passed all conducted testing. System "A" failed NCHRP Report 350 Test 2-11 due to vehicle override.  The Occupant Impact Velocities (OIV) and Occupant Ridedown Accelerations (ORA) for all other tests were below the preferred limits.  However, because your barrier is a "soft" system, deflections can be high and vehicles impacting the terminal at an angle can travel a significant distance behind the barrier.  Thus, it is important that all users be aware of deflection distance requirements and of the necessity to keep the area behind and beyond the terminal clear of workers and/or construction materials and equipment.

In summary, with the exception of system "A" above, the remaining systems described above (B & C) and detailed in the enclosed drawings are 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

Enclosures

Page last modified on January 17, 2013.
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