Does anyone know what the law is on using a modulating headlight on motorcycles?

I live in Utah, so that would be my primary concern, but curious about the law in general since we do travel out of state a lot!

Also would be interested in your opinion on using one.

I am pretty sure they are legal down here in Texas because I see lots on the road, especially out in the boonies.

They sure do help you see a bike coming so I'm sure they can help prevent someone from running in front of you.

Modualated headlights on motorcycles are addressed by federal law making them legal in all 50 states...

This Federal law supersedes all state laws and makes motorcycle headlight modulators legal in all 50 states.  FMVSS 108 (Federal Motor Vehicle Safety Standards) (49 CFR Part 571.108 S7.9.4) allows motorcycle headlight modulation systems all 50 states provided they comply with the standards set forth in this section.  

Title 49 USC 30103 (b1) (US Codes) prohibits any state from forbidding a system that conforms to FMVSS 108 (see copy below).  Here is a web page with all of Part 571 and all of the subsections; they've now broken it up by section to make it easier to read.  The Legal Information Institute at Cornell University also has a nice website where you can read the various sections of the entire Title 49 USC.

Code of Federal Regulations
Title 49, Volume 5, Parts 400 to 999
Revised as of October 1, 2000
From the U.S. Government Printing Office via GPO Access [CITE: 49CFR571.108] [Page 236-307]

TITLE 49	TRANSPORTATION
CHAPTER V	NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
PART 571	FEDERAL MOTOR VEHICLE SAFETY STANDARDS

Subpart B--Federal Motor Vehicle Safety Standards
Sec. 571.108 Standard No. 108;

Lamps, reflective devices, and associated equipment.

S7.9.4 Motorcycle headlamp modulation system.

S7.9.4.1 A headlamp on a motorcycle may be wired to modulate either the upper beam or the lower beam from its maximum intensity to a lesser intensity, provided that:

(a) The rate of modulation shall be 240 <plus-minus> 40 cycles per minute.

(b) The headlamp shall be operated at maximum power for 50 to 70 percent of each cycle.

(c) The lowest intensity at any test point shall be not less than 17 percent of the maximum intensity measured at the same point.

(d) The modulator switch shall be wired in the power lead of the beam filament being modulated and not in the ground side of the circuit.

(e) Means shall be provided so that both the lower beam and upper beam remain operable in the event of a modulator failure.

(f) The system shall include a sensor mounted with the axis of its sensing element perpendicular to a horizontal plane. Headlamp modulation shall cease whenever the level of light emitted by a tungsten filament light operating at 3000 deg. Kelvin is either less than 270 lux (25 foot-candles) of direct light for upward pointing sensors or less than 60 lux (5.6 foot-candles) of reflected light for downward pointing sensors. The light is measured by a silicon cell type light meter that is located at the sensor and pointing in the same direction as the sensor. A Kodak Gray Card (Kodak R-27) is placed at ground level to simulate the road surface in testing downward pointing sensors.

(g) When tested in accordance with the test profile shown in Figure 9, the voltage drop across the modulator when the lamp is on at all test conditions for 12 volt systems and 6 volt systems shall not be greater than .45 volt. The modulator shall meet all the provisions of the standard after completion of the test profile shown in Figure 9.

(h) Means shall be provided so that both the lower and upper beam function at design voltage when the headlamp control switch is in either the lower or upper beam position when the modulator is off.

S7.9.4.2(a) Each motorcycle headlamp modulator not intended as original equipment, or its container, shall be labeled with the maximum wattage, and the minimum wattage appropriate for its use. Additionally, each such modulator shall comply with S7.9.4.1 (a) through (g) when connected to a headlamp of the maximum rated power and a headlamp of the minimum rated power, and shall provide means so that the modulated beam functions at design voltage when the modulator is off.

(b) Instructions, with a diagram, shall be provided for mounting the light sensor including location on the motorcycle, distance above the road surface, and orientation with respect to the light.

Mike, I may be wrong, but from the little research I did it looks like this authority is used to mandate what safety equipment must be included in a vehicle manufactured in or imported to the US (i.e. all cars must HAVE seat belts, but the state determines the usage requirement), or what safety equipment CAN be used (i.e. modulating headlights) in ALL states.

But I don't believe this can be used to require the use of the equipment.

If you remember a couple years ago the NTSB called for all states to enact a mandatory helmet law because they didn't have the authority to do so (see http://www.cyclefish.com/BikerNews/blog/593/)

Like I said, I could be wrong

Dan, As for an opinion on running a modulated headlight, I believe anything you can do to make your motorcycle more conspicuous to other drivers can only be a good thing.

Got to agree with ya there BailOut.  I have done a lot to make my motorcycle more visible from the rear, but I'm thinking a modulating headlight can do a lot to be seen and noticed from the front.

Got these few pieces of info from the HURT report that pretty much say the same thing....

• In the multiple vehicle accidents, the driver of the other vehicle violated the motorcycle right-of-way and caused the accident in two-thirds of those accidents.
• The failure of motorists to detect and recognize motorcycles in traffic is the predominating cause of motorcycle accidents. The driver of the other vehicle involved in collision with the motorcycle did not see the motorcycle before the collision, or did not see the motorcycle until too late to avoid the collision.
• The most frequent accident configuration is the motorcycle proceeding straight then the automobile makes a left turn in front of the oncoming motorcycle they didn't see coming.
• Intersections are the most likely place for the motorcycle accident, with the other vehicle violating the motorcycle right-of-way, and often violating traffic controls.
• 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.

Guys...Thanks for the info there.....

I dont think we are allowed to have them headlights here in UK...but having said that...Every time I have been to USA I have seen the headlights from ALL angles and not just in the rear view mirrors and have obviously seen the bike from way off...

So for what its worth coming from a Fog Breathing Limey Brit I reckon they are worth their weight if just ONE PERSON was saved because of it.....

Now what I need to know is could they be made switchable between solid ON and modulated ON...is this possible?  Or would one fit into a spotlight?

Don't they effect how well you can see the road at night when the headlight is modulating (flashing)

All though I don't see it listed in the federal statue listed above, as far as I know no state allows a modulating headlight to be used at night! As a matter of fact just about every system I have seen comes with a sensor so the headlight only modulates during bright sunlight and at dusk automatically switches to standard operation (manual high/low beam controlled by the operator).

Plus they should have a manual override so you can turn the modulation off in case it is bright enough for the sensor not to kick in, but distracting to the rider (shaded ares, etc)

I shall now investigate for here...Thanks Lucky...

Good info. May have to look into this. I know on some of the long desert roads down here, even I have a hard time seeing a bike coming at me on a bright day, and I'm looking for them!

Does using a modulator on a headlight reduce the life of the lamp?

I imagine on a standard filament type headlight it might decrease the life slightly, but probably not that much. Turning a light on and off does decrease the life-span due to the filament heating and cooling. However since this is a very fast modulation I would think the filament temp would stay pretty constant.

It should have no effect on a Xenon headlamp since they have no filament.

I have sent an email to two of the companies that make modulators to get their input on this. I'll let you know what they say.

Did you ever get a response on this?  In my recent accident, the driver turned left across my lane without recognizing my presence.A headlight modulator may have made all the difference and I intend to put one on my new bike.  Does anyone have any recommendations? Or "real" advice?

 Just my two cents.  My uncle got his bike and it came stock with the modulated headlight.  A Suzuki 2006 or 2007 (I Boulevard I think,1300cc).  I asked him about driving at night but he also has a set of external lamps and said he did not notice it riding.  But riding in front of him it sure stuck out well.  Behind him in the day it was unnoticable.  His is on the left mine is on the right.

It is ILLEGAL in EVERY state to use a modulating headlight at night. Every system I have seen has a sensor so the headlight only modulates during daylight... I am sure his is not modulating at night if it is factory which is why he didn't notice any difference.