U.S. Department

of Transportation 400 Seventh St., S.W.

Federal Highway Washington, D.C.

20590

Administration

Refer to: HSA-10/WZ-94

Mr. Henry A. Ross, Director

Sales and Marketing

United Rentals Highway Technologies

880 North Addison Road

P.O. Box 7050

Villa Park, IL 60181-7050

Dear Mr. Ross:

Thank you for your letter of June 6 requesting Federal Highway

Administration (FHWA) acceptance of your company’s Low SafetyCor X-Tube

Speed Limit Sign structure as crashworthy traffic control devices 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 along with a video of the tests. 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.”

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 for which you are requesting acceptance follows:

The Low SafetyCor X-Tube Speed Limit Sign stand system is a lightweight portable sign support.

The support framework is made up of lightweight 44.5 mm square “X-Tube” PVC extrusions.

The X-Tube uprights slip into 57.2 mm perforated tube steel sockets welded to a support base.

The support base is made up of 50.8 mm x 50.8 mm x 4.8 mm thick steel angle iron. The sign

stand system features a three high arrangement of 914 mm wide rectangular signs made of 10.2

mm thick “SafetyCor,” an unfilled polypropylene copolymer corrugated plastic sheeting material. 
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Each sign is bolted to the uprights with four 7.9 mm diameter STM A307 hex fasteners and

special 38.1 mm outside diameter rubber encased flat washers that increase the bearing area and

help to prevent sign damage when the stands are stacked. The tested sign support was equipped

with two ToughLite 2000 Type A or B warning lights. The lights were attached to the top of the

support framework using standard tamper-proof warning light bolts. When deployed the bottom

of the sign is nominally 837 mm above the ground, and the overall height is 3405 mm to the top of

the lights. The mass of the supports, signs, and lights was 39.6 kg. Four 18 kg bags of sand were

added to the ends of the support base legs.

Testing

Full-scale automobile testing was conducted on your company’s devices. Two

stand-alone examples of the device were tested in tandem, one head-on and

the next placed six meters downstream turned at 90 degrees, as called for in

our guidance memoranda. The complete device as tested is shown in

Enclosure 1.

The crash test is summarized in the table below:

Test Number 05-3721-012

Test Article Low SafetyCor X-Tube Speed Limit

Sign

Height to Bottom of

Sign

837 mm

Height to Top of Lights 3405

Flags or lights Two ToughLite 2000s

Test Article Mass

(each)

39.6 kg

Vehicle Inertial Mass 823 kg

Impact Speed, Head-on 101.1 km/h

Impact Speed, 90 Deg. 96.4 km/h

Velocity Change, Headon1.4 m/s

Velocity Change, 90

deg.

1.3 m/s

Vehicle crush Slight damage to bumper, grille,

and hood

Occupant Compart.

Intrusion

None

Windshield Damage None

Findings

Damage was limited to slight denting to the bumper, grille, and hood. The device contacted the

windshield in both tests but caused no damage. The results of the testing met the FHWA
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requirements and, therefore, the devices described above and shown in the enclosed drawings for

reference are acceptable for use as Test Level 3 devices on the NHS under the range of conditions

tested, when proposed by a State.

Please note the following standard provisions which 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-94 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.

! United Rentals work zone traffic control devices may include patented components and if

so are 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.

 

Sincerely yours,

Frederick G. Wright, Jr.

Program Manager, Safety