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                Safety Eligibility Letter WZ-134
  
  **Hardware Type:**
            Work Zone Devices
                          **Code:**
            WZ-134
                          **Date:**
            03/04/2003
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            NYS DOT
                          **Device Description:**
            Temporary Lumber Sign Support
                          **View PDF:**
            wz134.pdf (976.52 KB)
    
    



March 4, 2003
Refer to: HSA-10/WZ-134
Mr. Larry W. Brown
New York State
Department of Transportation
Albany, New York  12232
Dear Mr. Brown:
Thank you for your letter of October 11, 2002, requesting
Federal Highway Administration (FHWA) acceptance of your state's temporary
lumber sign support as a crashworthy
traffic control device for use in work zones on the National Highway System
(NHS).  Accompanying your letter were
drawings of the support and a verbal comparison to a similar crash tested
support. You requested that we find this device 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.” You provided additional information, including drawings, on
February 24, 2003.
Introduction
The FHWA guidance on crash testing of work zone traffic
control devices is contained in two memoranda. 
The first, dated July 25, 1997, titled “INFORMATION: Identifying
Acceptable Highway Safety Features”, established four categories of work zone
devices: Category I devices were those lightweight devices which could be
self-certified by the vendor, Category II devices were other lightweight
devices which needed individual crash testing, Category III devices were
barriers and other fixed or massive devices also needing crash testing, and
Category IV devices were trailer mounted lighted signs, arrow panels, etc.  The second guidance memorandum was issued on
August 28, 1998, and is titled “INFORMATION: Crash Tested Work Zone
Traffic Control Devices.”  This later
memorandum lists devices that are acceptable under Categories I, II, and III.
A brief description of the device\s follows:
The NYS DOT Temporary Lumber Sign Support consists of
two 8-foot long uprights of nominal 2x4 inch lumber.  The skids are also 2x4 inches and are 48 inches long.  The diagonals are also 2x4s.  The crash tested support, as detailed in
FHWA Acceptance Letter WZ-3 dated August 28, 1998, uses 4x4 inch uprights that
are 9 feet long, and 2x6 inch skids that are 72 inches long. The
tested support also uses 2x4 inch diagonals, but only one pair on the
downstream side of the uprights.
The cross section of the uprights and skids of the NYS DOT
support are smaller than the crash tested support and are likely to result in
equal or better performance than the tested support. Drawings of your sign
stand, in English and Metric units, are enclosed for reference. The only significant differences between the NYS DOT support and the
tested support that could lead to poor performance are the height of the
uprights and the presence of four diagonal braces, as discussed below:
Height of sign: The tested device used 9 foot long
uprights and supported the sign at a height of 5 feet above the pavement. At this height, the head-on test allows the
sign to pass over the vehicle with little or no contact. At the 90 degree hit, however, the corner of
the sign does contact the roof and cause minor deformation. If the sign is mounted any lower it is
possible that the edge of the sign could impact the windshield and cause
unacceptable damage. Therefore it is
important that 48x48 diamond signs are mounted at a minimum height of 5 feet to
the bottom, and other size/shape signs be mounted as high on the support as
possible. This is noted on your
drawing.
Diagonal bracing: The tested support used one pair of
diagonals on the downstream side of the uprights. This is the most critical location as the tops of the braces are
“aimed” towards the impacting vehicle. No tendency for the diagonals to exacerbate the damage was noted.  In the NYS DOT design, the second pair of
diagonal braces is in a position to be struck first by the vehicle and knocked
down and out of harm's way. Therefore
the extra braces should not adversely affect the performance of the stand.Findings
Because the NYS DOT temporary lumber sign support is
comparable to the tested lumber sign stand, it may also be considered
crashworthy with the restriction that the signs must be mounted at a minimum
height of 5 feet from the ground (for diamond signs.  Rectangular signs must be mounted as high as practical.)  Therefore, the sign stand described above
and shown in the enclosed drawings for reference is acceptable for use as a
Test Level 3 device on the NHS under the range of conditions the comparable
sign was tested, when proposed by a State.
Please note the following standard provisions that apply to
FHWA letters of acceptance:
Our 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, it reserves the
right to modify or revoke its acceptance.
You will be expected to
supply potential users with sufficient information on design and installation
requirements to ensure proper performance.
The fabricator will be
expected to certify to potential users that the hardware furnished has
essentially the same mechanical properties and geometry as that submitted for
acceptance, and that they will meet the crashworthiness requirements of FHWA
and NCHRP Report 350.
To prevent
misunderstanding by others, this letter of acceptance, designated as number
WZ-134 shall not be reproduced except in full. 
This letter, and the test documentation upon which this letter is based,
is public information. All such letters and documentation may be reviewed at
our office upon request.Sincerely yours,
Michael S.
Griffith
Acting
Director, Office of Safety Design
Office of Safety U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

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