Mr. Paul Lang
Lang Products International
1870 E. 50th Street
Inver Grove Heights, Minnesota 55077
Dear Mr. Lang:
Thank you for your letters of March 26,
2002 and July 12, 2002, to
Mr. Nick Artimovich of my office requesting
Federal Highway Administration (FHWA) acceptance of your company=s
LTT-1 portable sign stand as a crashworthy
traffic control device for use in work zones on the National Highway System
(NHS). Accompanying your letter was a report of crash testing conducted by
E-Tech Testing Services, Inc. and a video of the tests. You requested that
we find this stand 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 also requested
acceptance of numerous variations in sign size, shape, material, attachment
methods, etc., some of which are discussed under "findings" below.
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 AINFORMATION:
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 follows:
The LTT-1 portable sign consists of a 1220 x 1220 mm (48 x 48 inch) diamond
shaped 12.7 mm (½ inch) thick MDO plywood sign attached to 44.5 mm square,
2.7 mm thick (1 ¾ inches x 12 ga) perforated square steel tube uprights
supported by 50.8 mm square, 3.0 mm thick (2 inches x 11 ga) steel tube removable
arched legs. The uprights are secured onto the arched legs by a 22 inch x 1.5
inch x 1.5 inch x 3/16 inch receiver stud that fits inside the lower portion
of the uprights. This stud is permanently welded onto the arched leg in a perpendicular
orientation. All tubing is ASTM A500 Grade B steel. The fasteners are 76.2 mm
(3 inch) long 7.9 mm (5/16 inch) grade 5 bolts secured by nylon insert lock
nuts. The height of the bottom tip of the sign was a nominal 304.8 mm (12 inches)
above ground level.
Full-scale automobile testing was conducted on your company=s devices. Two
stand-alone examples of the device were tested individually; one at a 90 degree
orientation and the next was impacted head-on. The complete device as tested
is shown in Enclosure 1. In the test report, the device is identified as "SF-R48,"
a designation you have changed to "LTT-1". The crash test is summarized
in the table below:
Long Term Temporary Sign
Height to Bottom of Sign
Height to Top of Sign
Flags or lights
Test Article Mass (each)
kg, plus four 16 kg sandbags
Vehicle Inertial Mass
Impact Speed, Head-on
Impact Speed, 90 Deg.
Velocity Change, Head-on
Velocity Change, 90 deg.
crease to hood
to hood and grille
touched, no cracks
Damage was limited to sheet metal damage
of the hood, and damage to the bumper and grille of the test vehicle. Velocity
change for the 90 degree test was in the "acceptable" range while the velocity
change for the head-on impact was in the "desirable" range. The results of
the testing met the FHWA requirements and, therefore, the devices described
above and shown in the enclosed drawings for reference are acceptable for use
on the NHS under the range of conditions tested, when proposed by a State.
Variations to the devices as tested
A number of variations
to the tested sign and support were included in your March 26, 2002, letter
with a request that they be considered acceptable. We concur that the following
variations are also acceptable for use (except as noted below):
- Sign substrates. The tested
sign was 48 x 48 x 0.5 inch MDO plywood that weighed approximately 25 pounds.
You requested the following variations be accepted:
- All types and grades of ½ inch
- All rigid substrates of lesser
mass, including 0.100 inch and 0.080 inch aluminum.
- All semi rigid substrates for
which we have testing history, including Endurance (Lexan), Coroplast
(Safety Core, SafetyPlast), Alpolic, Renolite, Dibond and Alumalite (aluminum
- plastic laminates).
- Use of two signs, back to back,
when the combined weight of the two signs does not exceed 25 pounds.
- Use of 36 x 36 inch sign blanks
of any rigid or semi rigid material when the mass of the sign does not
exceed 25 pounds. This includes back-to back signs. The heaviest single
sign in this size is ¾ inch plywood which weighs 19 pounds. These smaller
signs are to be mounted such that their center is at the same height as
the tested 48 x 48 inch signs.
- Sign shapes. The tested sign
was a 48 x 48 inch diamond which has a diagonal measurement of approximately
67.5 inches. You requested that other shapes be acceptable providing:
- The mass does not exceed 25 pounds,
the top of the sign does not exceed 80 inches (approximate height of tested
sign), and the center of the sign is set at 45 to 47 inches (as
was the tested sign.) The following signs were specifically requested:
- STOP signs, YIELD signs, or square
signs with a maximum dimension of 48 inches.
- Vertical rectangles with a maximum
vertical dimension of 60 inches.
- Horizontal rectangles with a maximum
horizontal dimension of 60 inches.
- Combination or multi-panel signs,
such as detour assemblies with a route marker and a direction indicator
- Sign attachment bolt pattern.
The tested signs were fastened with a 24 inch square bolt pattern. You requested
the following variations to that pattern:
- Variations that include a maximum
horizontal dimension of 48 inches and a minimum of 18 inches; maximum
vertical dimension of 36 inches and a minimum of 12 inches.
- Variations that include more than
- Variations for the 36 x 36 inch
diamond, and other shapes/sizes discussed above.
- Upright locking hardware.
The tested signs used 5/16 inch x 3 inch long grade 5 zinc plated hex bolts
to secure the leg assembly into the upright tubes. The bolt was secured with
a nylon insert lock nut. You requested the following variations:
- [4a. and 4b. Your request referred
to eliminating the nut for bolts (screws) that penetrate the upright tube.
Upon further discussion you retracted that request.]
- Any grade 5 bolt or better, with
a diameter greater than 5/16 inch.
- Optional use of quick release
snapper pins, hitch pins, and cotter pins.
- Use of non-locking nuts and wing
nuts as alternate hardware.
- Sign attachment hardware. The
tests used four 5/16 inch x 3 inch x grade 5 hex bolts for attaching the signs
to the uprights. The top washer was a standard cut iron washer, and the second
was a 1.25 inch fender washer that was 0.062 thick. You requested the following
- Bolts of 5/16 inch diameter in
- Bolts of 3/8 inch diameter in
- Fender washers of up to 1 ½ inch
- Use of alternative lock nuts,
such as center lock nuts, castle lock nuts, top lock nuts, and the use
of lock washer for securing the sign attachment hardware.
- Use of conventional (non-locking)
hex nuts, square nuts, and wing nuts.
- As requested in your July 12,
2002, letter, "rubber bumpers" may be used in lieu of flat washers.
- Upright Tube Member. The tested
stands used 1 ¾ inch square, 12 gage Telespar uprights, with 7/16 inch holes
spaced at 1 inch centers. You requested the following variations:
- Use of non-perforated 1 ¾ inch
square, 12 gage Telespar uprights.
- Use of 1 ¾ inch square 12 gage
structural tubing as an alternative to the Telespar tubes.
- The top of the "receiver stud"
may be cut at an angle to facilitate assembly as requested in your July
12, 2002, letter.
- Sand Bag Request. The tested
stand was ballasted by four 35 pound sand bags. You requested the option to
- Up to 8 sand bags, (two per foot.)
- Varying weights of sand bags from
20 pounds to 50 pounds (to a maximum of 300
- Sign Sheeting. The sign substrates
were faced sheeted with 3M Diamond Grade with 3M Scotchcal legend. You requested
the use of alternative retroreflective sheeting, or the use of signs without
- Production Modifications for Leg
Tube. The 2 x 2 inch leg tube used in the tests did not include any perforations
or embossed/stenciled identification. You requested that rain drainage holes
and embossed/stenciled identification marks be accepted. These are acceptable
as discussed in your July 12, 2002, letter.
You also spelled out
three scenarios for the use of these stands that are beyond the scope of laboratory
crash testing and asked that your stand be listed as "exempt" from the need
for additional testing. It has been our policy that the crash testing of devices
according to NCHRP Report 350 is meant to discriminate between devices when
tested "on a level playing field," both figuratively and literally. We recognize
that there are many situations in the "real world" highway environment where
the tested devices may be in use and, because of topography or the presence
of other road features, may not perform as they did when tested. As we do not
require testing for these scenarios, there is no need for specific waivers for:
- Mounting of the sign stand on a slow-moving
- Use of longer legs when the sign stand
straddles a median barrier.
- Use on stepped or sloped terrain
where one leg has to be made longer in order to present a level sign.
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.
- You will be expected to certify to potential users that the hardware furnished
has essentially the same chemistry, 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-126 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.
- The Lang Products International Long Term Temporary SF-R48 sign is in patent
- pending status product and may be considered "proprietary." The
use of proprietary work zone traffic control devices in Federal-aid projects
is generally of a temporary nature. They are selected by the contractor for
use as needed and removed upon completion of the project. Under such conditions
they can be presumed to meet requirement "a" given below for the
use of proprietary products on Federal-aid projects. On the other hand, if
proprietary devices are specified for use on Federal-aid projects, except
exempt, non-NHS projects, they: (a) must be supplied through competitive bidding
with equally suitable unpatented items; (b) the highway agency must certify
that they are essential for synchronization with existing highway facilities
or that no equally suitable alternative exists or; (c) they must be used for
research or for a distinctive type of construction on relatively short sections
of road for experimental purposes. Our regulations concerning proprietary
products are contained in Title 23, Code of Federal Regulations, Section 635.411,
a copy of which is enclosed.
Carol H. Jacoby, P.E.
Director, Office of Safety