Motorcycle Headlamp Modulator
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A Motorcycle Headlight Modulator (or simply Headlight Modulator) is an accessory device that oscillates the intensity of a daytime-illuminated motorcycle headlamp at 240 cycles per minute (4 Hz). The intensity is modulated between approximately 20% and 100% of normal steady-burning intensity. The headlight operates at full intensity 50-70% of the time. US and Canadian regulations require headlight modulators to include a light sensor that disables modulation when the ambient light level drops below a certain point. When this happens, the headlamps burn steadily.
[edit] Purpose
Motorcycles in the United States have since the mid-1970s been wired so as to operate the low beam headlamp whenever the engine is running. This is not required by any Federal regulation, but is rather a matter of voluntary industry policy. The Hurt Study found “Conspicuity of the motorcycle is a critical factor in the multiple vehicle accidents, and accident involvement is significantly reduced by the use of motorcycle headlamps (on in daylight) and the wearing of high visibility yellow, orange or bright red jackets” and “Conspicuity of the motorcycle is most critical for the frontal surfaces of the motorcycle and rider”. However, as increasing numbers of vehicles are equipped with daytime running lights, there is concern that the daytime-illuminated motorcycle headlamp may no longer provide a significant conspicuity benefit. Therefore, some motorcyclists install headlamp modulators in the belief they increase motorcycle conspicuity in traffic.
[edit] Science
While there are no studies supporting the headlamp modulator as an effective motorcycle safety device, there have been some studies suggesting headlamp modulators may increase the conspicuity of motorcycles:
- "Olson, P L, Halstead-Nussloch, R and Sivak, M (1979) Development and testing of techniques for increasing the conspicuity of motorcycles and motorcycle drivers. Final report" ([1]) "The results indicate that daytime conspicuity can most effectively be improved by use of fluorescent garments or steady or modulating lights."
- "Florida Highway Patrol Emergency Lighting Research & Prototype Evaluation March 2004" ([2]). While this study was performed to determine the best lighting to protect law enforcement officers, it examines how motorist react to various lighting on vehicles. This study suggests "...flashing lights are more conspicuous than steady lights".
[edit] Laws about Headlamp Modulators
In the United States, FMVSS 108 (Federal Motor Vehicle Safety Standards) (49 CFR Part 571.108 S7.9.4) allows motorcycle headlamp modulation systems in all 50 states provided they comply with the standards set forth in this section. Furthermore, Title 49 USC 30103(b1) (US Code) prohibits any state from forbidding a system that conforms to FMVSS 108. The Code of Federal Regulations (CFR) is available at [3]. In the search enter 49 for Title, 571 for Part and 108 for Section. The paragraph that discusses motorcycle headlight modulation systems is S7.9.4. The United States Code (USC) is available at [4]. In the search enter 49USC30103
In Canada, Technical Standards Document No. 108, Revision 3 Lamps, Reflective Devices and Associated Equipment contains language nearly identical to the US code. The code is available at [5]. Scroll down the page (or use the search in your browser) and locate paragraph S7.9.4
