A motorcycle headlamp modulator (or simply headlamp modulator) is an accessory device that oscillates the intensity of a
motorcycle
A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruisin ...
headlamp
A headlamp is a lamp attached to the front of a vehicle to illuminate the road ahead. Headlamps are also often called headlights, but in the most precise usage, ''headlamp'' is the term for the device itself and ''headlight'' is the term f ...
at 240 ±40 cycles per minute (~4 Hz) between approximately 20% and 100% of full intensity. The headlight operates at full intensity 50-70% of the time. United States 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.
Purpose
Motorcycles in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...
since 1978 have been wired so as to operate the low-beam headlamp whenever the engine is running. This is not required by any federal regulation but rather is a matter of voluntary industry policy. However, as increasing numbers of vehicles are equipped with
daytime running light
A daytime running lamp (DRL, also daytime running light) is an automotive lighting and bicycle lighting device on the front of a roadgoing motor vehicle or bicycle, automatically switched on when the vehicle's handbrake has been pulled down, ...
s, daytime-illuminated motorcycle headlamp may no longer provide a significant
conspicuity benefit. Some motorcyclists install headlamp modulators in the belief they increase motorcycle conspicuity in traffic.
Science
While there are no studies supporting the headlamp modulator as an effective motorcycle safety device, some research suggests headlamp modulators may increase the conspicuity of motorcycles.
I would suggest to read the Hurt Report https://en.wikipedia.org/wiki/List_of_findings_in_the_Hurt_Report
The report highly suggest that Headlight modulation improves the visibility of a motorcycle to oncoming traffic
Laws about Headlamp Modulators
North America
In the United States,
Federal Motor Vehicle Safety Standard 108 Federal Motor Vehicle Safety Standard 108 (FMVSS 108) regulates all automotive lighting, signalling and reflective devices in the United States. Like all other Federal Motor Vehicle Safety Standards, FMVSS 108 is administered by the United States ...
, which regulates all
automotive lighting
The lighting system of a motor vehicle consists of lighting and signalling devices mounted to or integrated into the front, rear, sides, and in some cases the top of a motor vehicle. They illuminate the road ahead for the driver and increase th ...
devices and systems, permits motorcycle headlamp modulation systems provided they comply with the performance, operation, and durability requirements contained therein Canada's analogous regulation, Canada Motor Vehicle Safety Standard 108, likewise permits headlamp modulators that meet the same technical requirements as those in force in the USA.
Canada Motor Vehicle Safety Standard 108; TSD 108 S7.9.4
See also
* Headlight flashing
Headlight flashing is the act of either briefly switching on the headlights of a car, or of momentarily switching between a headlight's high beams and low beams, in an effort to communicate with another driver or drivers. The signal is sometime ...
* Wig-wag (automobile)
References
{{Reflist
Headlight modulator
Vehicle safety technologies
Motorcycle safety