[2] 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.
Motorcycles in the United States since 1978 have been wired so as to operate the low-beam headlamp whenever the engine is running[citation needed].
However, as increasing numbers of vehicles are equipped with daytime running lights, daytime-illuminated motorcycle headlamps may no longer provide a significant conspicuity benefit.
Some motorcyclists install headlamp modulators in the belief they increase motorcycle conspicuity in traffic.
[3] In the United States, Federal Motor Vehicle Safety Standard 108, which regulates all automotive lighting devices and systems, permits motorcycle headlamp modulation systems provided they comply with the performance, operation, and durability requirements contained therein[4] 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.