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U.S. Department of Transportation

Federal Highway Administration

400 Seventh St., S.W.
Washington, D.C. 20590


December 1, 2004

Refer to: HSA-10/WZ-195

Dr. Ron Faller, Research Assistant Professor
Midwest Roadside Safety Facility
University of Nebraska - Lincoln
527 Nebraska Hall
P.O. Box 880529
Lincoln, Nebraska 06588-0529

Dear Dr. Faller:

Thank you for your letter of October 22, 2004, requesting Federal Highway Administration's (FHWA) acceptance of the Intellistrobe Portable Traffic Control Signal System as a crashworthy traffic control device for use in work zones on the National Highway System (NHS). Accompanying your letter were reports of crash testing you conducted, and video of the tests. You requested that we find these devices 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."


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 are those lightweight devices which are to be self-certified by the vendor, Category II devices are other lightweight devices which need individual crash testing but with reduced instrumentation, Category III devices are barriers and other fixed or heavy devices also needing crash testing with normal instrumentation, and Category IV devices are trailer mounted lighted signs, arrow panels, etc. for which crash testing requirements have not yet been established. 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 follows:

The device's base is Grade 3003 aluminum and measures 36.25 inches tall by 12 inches deep and 16 inches wide. The wall thickness is 0.0875 inch. Hinged, extendable legs are used to level the device and to provide stability. The upper portion of the aluminum legs is 1.5 inches square and 24 inches long. The lower part is steel and measures 1.0 inches square and 16.5 inches long.

The vertical upright support is 2.0 inch square, Grade 3003 aluminum tubing with 0.125 inch wall thickness. It is 12 inches long and is welded to the base unit. The vertical mast is 1.5 inch square Grade 3003 aluminum tubing with 0.125 inch wall thickness. It slides inside the 2.0 inch support and is fastened in place with a 3.0 inch long keeper pin. The signal head assembly is a plastic case housing two 12-inch diameter LED lamps.

The height to the top of the signal base is 37.25 inches, and the height to the top of the signal head is approximately 135 inches. The weight of the base plus battery is 93 pounds while the mast with signal head weighs 19 pounds.


Bogie testing was conducted on the Intellistrobe devices, with one system being struck in each impact.

The tests are summarized in the table below:


Intellistrobe portable traffic control signal system

Test Number




Version Tested





End on

Head on

Head on

Mounting heights – to top

135 in

135 in

134.5 in

Weight of Tested Stand

112 pounds

112 pounds

120 pounds

Mass of Bogie

2467 pounds

Impact Speed

98.0 km/hr

99.3 km/hr

100.7 km/hr

Velocity Change

1.2 m/s

1.2 m/s

1.3 m/s

Extent of contact

None in windshield area

Portion of leg impacted windshield

None in the windshield area

Other notes

Acceptable performance

Windshield contact led to redesign

Acceptable performance

This crash-testing program used a hard-nosed bogie vehicle of a mass larger than the standard 820C test vehicle. There are significant constraints involved in using such a non-standard testing device, some of which are:

  1. The potential vehicle velocity change must be considered insignificant.
  2. The crush characteristics of an automobile bumper must not be expected to have a significant affect on the trajectory of the test article.
  3. The profile of the bogie vehicle must be configured to replicate the outline of a production vehicle. The MwRSF bogie was configured to replicate the outline of a Geo Metro, a vehicle commonly used in testing of work zone devices.
  4. No part of the test article may intrude into the windshield area of the vehicle after impact.

In the present testing, test IS-3 resulted in a portion of a leg break loose and contacting the windshield area of the bogie vehicle. Upon redesign of the leg attachment and running of a retest, test IS-5, the device performed satisfactorily as the legs remained attached to the base cabinet.


The results of the testing met the FHWA requirements and, therefore, the portable traffic control device described above and detailed in the enclosed drawings is acceptable for use on the NHS under the range of conditions tested, when proposed by a State.

Please note the following standard provisions that apply to FHWA letters of acceptance:

Sincerely yours,

/Original Signed by H. Kalla/

John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety


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