Interpretation ID: 1982-1.11
TYPE: INTERPRETATION-NHTSA
DATE: 02/09/82
FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA
TO: United Sidecar Association, Inc.
TITLE: FMVSS INTERPRETATION
TEXT: This is in reply to your letter of September 9, 1981, asking several questions about Federal Motor Vehicle Safety Standard No. 108.
You have asked for a clarification of our position on pulsating headlamps and stoplamps commenting that several States have expressed a concern "that a light of variable intensity may be confused by the citizen as an emergency vehicle which is allowed to have flashing headlights."
As you have indicated, paragraph S4.6(a) of Standard No. 108 requires turn signal lamps, hazard warning signal lamps, and school bus warning lamps to flash when activated, while S4.6(b) requires all other lamps to be steady burning. By "steady burning," the standard means a light that is essentially unvarying in intensity. There is, however, an exception in S4.6(b) to the "steady burning" requirement. Means may be provided "to flash headlamps and side marker lamps for signalling purposes." Paragraph S3 of the standard defines "flash" as meaning "a cycle of activation and deactivation of a lamp by automatic means. . . ." In our view, a lamp whose intensity varies from a higher output to a lower output would not be "steady burning" or "flash" within the meaning of those terms and hence would be prohibited. But if complete deactivation occurs, then the lamp "flashes." Installation of flashing lamps under the S4.6(b) exception is not restricted to emergency vehicles. It is permissible under the standard for a motorcycle to have a device which gives the motorcyclist the option of causing the motorcycle headlamp to operate automatically through cycles of activation and deactivation instead of burning steadily.
On the other hand, stop lamps that either flash or are of variable intensity are not allowed by S4.6(b) of Standard No. 108 since they are not steady-burning while in use.
I hope this answers your questions.
SINCERELY,
United Sidecar Association, Inc.
September 9, 1981
Office of the Chief Counsel NHTSA
Gentlemen:
We are quite perplexed regarding the legality or otherwise of certain devices used in lighting circuits of motorcycles. Specifically, we refer to devices to flash or modulate or pulsate the light intensity, whether for headlights, or for stop lights.
As we understand FMVSS 108, all lights installed on a motor vehicle must be STEADY BURNING with the sole exception being turn signal lamps, hazard warning signal lamps, school bus warning lamps and various lamps used by police and emergency vehicles.
It is also our understanding that steady is equivalent to uniform, stable, not shaky, regular, continuous, uniform and constant. In other words, a steady light is one that does not flash, pulsate, or is otherwise discontinuous or variable in intensity.
Many devices are now offered for sale that cause the headlight to vary in intensity. Others are available to pulsate or blink the stop light. The purported purpose of these devices is to attract more attention to the light. And, if so, the user is alleged to be safer. However, several Departments of Public Safety have expressed a concern that a light of variable intensity may be confused by the citizen as an emergency vehicle which is allowed to have flashing headlights.
The citizen will not readily recognize the subtle difference between a pulsating headlight or a modulating headlight or a flashing headlight. When he sees a flashing headlight will he respond as if it were an emergency vehicle or as just another motorcycle?
AS we understand from verbal communications with NHTSA officials, a pulsating headlight is a steady light but a pulsating stop light is not a steady stop light.
This is indeed most perplexing and confusing.
If the pulsating headlight is steady, then it would not appear to require State legislation for its use. If it is not steady then it is prohibited under FMVSS 108. If the pulsating headlight is steady, then it can be used for any application. If not, it can be used for none.
We are anxious to promote the safety and well being of our members. However, we cannot and will not promote any device that appears to be illegal and in contravention to State or Federal regulations.
We urge, with utmost expediency, a full and complete definition of exactly what is and what is not a steady, burning light. Also, what type of devices, if any, have been approved by NHTSA and by the appropriate regulatory bodies for varying the intensity of the headlight and the stop light.
If a device that varies the intensity of the headlight at 3 to 5 Hz is legal, then is a device that varies the headlight at 0.75 to 1.5 Hz legal if some voltage is always applied to the light bulb? Also, what criteria is legal for variable intensity stoplights?
H. A. Kendall, Ph.D.