October 17,2002

Refer to: HSA-10/SS-113

Mr. Frank Hurt
Intellistrobe Safety System
1315 East Montclair
Springfield, Missouri 65804

Dear Mr. Hurt:

Thank you for your recent letter requesting Federal Highway Administration (FHWA) acceptance of your company's Intellistrobe signal system as a breakaway sign support system for use on the National Highway System (NHS). Accompanying your letter was a report from Karco Engineering and videos of the crash tests. You requested that we find the Intellistrobe system 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." On September 19, we received additions and corrections to your original submission.


Except for the mass of the test vehicle, testing of the breakaway signal system was in compliance with the guidelines contained in the NCHRP Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. Requirements for breakaway supports are those in the American Association of State Highway and Transportation Officials' (AASHTO) Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals. The vehicle mass is discussed in the following section.


The test article was a 4 x 4 inch treated wood post supporting a 36 x 36 inch reflective aluminum sign. Behind the sign was a 6 x 10 x 4 inch electronic module that powered a 12 inch diameter flashing yellow light. Atop the installation was a solar collector panel measuring 11 inches x 18 inches. The enclosed drawings show the Intellistrobe assembly as tested. The weight of the receiver/light assembly was 36 pounds.

Full-scale automobile testing was conducted on your company=s device. The mass of the test vehicle was 887 kg in the test. Although this mass exceeds the tolerance (820 kg +/- 25 kg) contained in NCHRP Report 350, the resulting velocity changes were so low as to indicate that the system would have passed the test had a vehicle conforming to the 820C specifications been used.

The test vehicle's speed at impact was 35.3 km/hr. The vehicle velocity change during the impact was 1.8 km/hr, or 0.5 m/s. The occupant ridedown acceleration was 0.2 g's, and there was no occupant impact speed. At impact, the wood support fractured at two places - at the groundline and approximately 32 inches above ground. The support and the signal assembly rotated over the vehicle, lightly contacting the roof. There was no deformation of the roof, and no intrusion into the vehicle occupant compartment.


Damage was limited to contact marks on the rear of the roof, with no windshield contact occurring. Velocity changes were all within acceptable limits, and the only stub remaining was broken off just below the ground. The results of testing met the FHWA 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.

You also requested that the Intellistrobe be acceptable when mounted on a 4 x 6 inch wood post in addition to the 4 x 4 it was tested on. Breakaway 4 x 6 wood posts are typically weakened with 1.5 inch holes drilled in the center of the 6-inch wide face, located at 4 inches and 18 inches above the groundline to facilitate fracture. The Intellistrobe hardware may be mounted on a 4 x 6 wood post when these holes are drilled as specified.

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

Sincerely yours,


Carol H. Jacoby, P.E.
Director, Office of Safety Design