Interpretation ID: GF006498

Mr. Jack W. DeYoung
Tumbleweed Trucks, Inc.
318 Kwanzan Drive
Lynden, WA 98264

Dear Mr. DeYoung:

This responds to your facsimile dated August 29, 2003, seeking further clarification of our interpretation letter sent to you on August 7, 2003. In response to our August 7^th letter, you have reprogrammed the flash rate in your hazard warning signal flasher. You now ask whether the newly reprogrammed flash rate complies with the requirements of Federal Motor Vehicle Safety Standard No. 108 (Standard No. 108).

By way of background, the National Highway Traffic Safety Administration (NHTSA) does not provide approvals of motor vehicles or motor vehicle equipment. Under 49 U.S.C. Chapter 301, manufacturers are required to certify that their vehicles and equipment meet applicable requirements.

As previously discussed, SAE Recommended Practice J945, "Vehicular Hazard Warning Signal Flasher," February 1966 (SAE 945), is incorporated by reference in Standard No. 108, as the Federal Requirement for Flashers. Paragraph 3 of J945 and its accompanying Figure 1 specify requirements for "Flash Rate and Percent Current On Time." The flash rate must be 60 to 120 flashes per minute for "normally open" (i.e., variable load) flashers, and 90 to 120 flashes per minute for "normally closed" (i.e., fixed load) flashers. This paragraph also specifies that:

"flashing rate . . . shall be measured after the flashers have been operating for a minimum of five consecutive cycles and shall be an average of at least three consecutive cycles." (emphasis added)

Your newly reprogrammed flash pattern operates as follows (in milliseconds):

Our calculations indicate that the above flash pattern, taking into account the averaging procedure set forth in J945, is within the specified flash rate.

In considering this issue further, however, we believe this type of flash pattern is very different from what NHTSA contemplated in incorporating J945 by reference in Standard No. 108. As you know, existing flashers operate at an essentially constant rate. Moreover, while Figure 1 of J945 permits considerable flexibility in flash rate, our calculations indicate that the flash rate and percent current on time for each and every cycle of your flash pattern fall outside the figure.

As we have stated before, we believe that motor vehicle safety is best promoted by standardization of lighting signals. The information currently provided by signal lamps, such as flashers, is well understood by the driving public, instantly recognized, and unambiguously informative. We are concerned that very different flash patterns have the potential to cause confusion. Therefore, we plan in the near future to modify Standard No. 108 in a way that would preclude your design.

If you need further assistance, please contact George Feygin of my staff at this address or at (202) 366-2992.

Sincerely,

Jacqueline Glassman
Chief Counsel

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