https://www.gpo.gov/fdsys/pkg/CFR-20...sec571-108.xml

S5.5.11(a) Any pair of lamps on the front of a passenger car, multipurpose passenger vehicle, truck, or bus, whether or not required by this standard, other than parking lamps or fog lamps, may be wired to be automatically activated, as determined by the manufacturer of the vehicle, in a steady burning state as daytime running lamps (DRLs) and to be automatically deactivated when the headlamp control is in any “on” position, and as otherwise determined by the manufacturer of the vehicle, provided that each such lamp1) Has a luminous intensity not less than 500 candela at test point H-V, nor more than 3,000 candela at any location in the beam, when tested in accordance with Section S11 of this standard, unless it isi) A lower beam headlamp intended to operate as a DRL at full voltage, or at a voltage lower than used to operate it as a lower beam headlamp; or(ii) An upper beam headlamp intended to operate as a DRL, whose luminous intensity at test point H-V is not more than 7,000 candela, and which is mounted not higher than 864 mm above the road surface as measured from the center of the lamp with the vehicle at curb weight;(2) Is permanently marked “DRL” on its lens in letters not less than 3 mm high, unless it is optically combined with a headlamp;(3) Is designed to provide the same color as the other lamp in the pair, and that is one of the following colors as defined in SAE Standard J578 MAY88: White, white to yellow, white to selective yellow, selective yellow, or yellow;(4) If not optically combined with a turn signal lamp, is located so that the distance from its lighted edge to the optical center of the nearest turn signal lamp is not less than 100 mm, unlessi) The luminous intensity of the DRL is not more than 2,600 candela at any location in the beam and the turn signal meets the requirements of S5.3.1.7; or(ii) (For a passenger car, multipurpose passenger vehicle, truck, or bus that is manufactured before October 1, 1995, and which uses an upper beam headlamp as a DRL as specified in paragraph S5.5.11(a)(1)(ii)) the luminous intensity of the DRL is greater than 2,600 candela at any location in the beam and the turn signal lamp meets the requirements of S5.3.1.7; or(iii) The DRL is optically combined with a lower beam headlamp and the turn signal lamp meets the requirements of S5.3.1.7; or(iv) The DRL is deactivated when the turn signal or hazard warning signal lamp is activated.

 

Well if you really want to know this is the definitive specification that is utilized. As usual from what I have seen above it is not accurate. This is why the cheap lights are not and it is a self certification to "DOT" as you may see on a external face of the light. Every manufacturer who tests to the following standard will mark the light with a "DOT" on it is voluntary but all do because they want you to know in order to sell more lights and yes THE TESTING IS EXPENSIVE to do. It is the link because it is much to voluminous to post the entire content here.

For those of you that are interested in learning about this : https://www.ecfr.gov/cgi-bin/text-id...e49.6.571_1108

 

I posted the section a out headlights above. You and I posted the same thing. The law only calls for max candela. As long as the lights are blow the max at their most intense section, then they are good.

 

Holy scrollfest! But I also thought as you that most any maker is going to mark stuff DOT "compliant" or whatever term they want to use until some agency actually calls them out on it and makes them stop. Meanwhile the motoring public takes the packaging at face value.

 

 

The problem here is there are a ton of people saying adding LEDs is illegal. It may be in their state, but you can't throw a blanket statement out there and not back it up with facts. The fact is that as long as the light intensity isn't above the DOT mandate then they are legal. What your state does is up to the state..

 

You would be incorrect sir. At least in Texas. Same goes if you are on a "public road" with a non DOT tire.. Need to do more due diligence on this.

 

 

Well you would be incorrect. The specifications that are called out in many other instances of this regulation or comprehensive. You cherry picked one thing when in fact, there is a plethora of pertinent specifications imbedded within that document that are applicable.

 

Show me the section that backs your stance.

 

Here is another "cherry picked" section that states the same thing


S14.2.1.6 Bulbs. Except for a lamp having a sealed-in bulb, a lamp must meet the applicable requirements of this standard when tested with a bulb whose filament is positioned within ±.010 in of the nominal design position specified in SAE Recommended Practice J573d (1968) (incorporated by reference, see §571.5) or specified by the bulb manufacturer and operated at the bulb's rated mean spherical candela.

S14.2.1.6.1 Each lamp designed to use a type of bulb that has not been assigned a mean spherical candela rating by its manufacturer and is not listed in SAE Recommended Practice J573d (1968) (incorporated by reference, see §571.5), must meet the applicable requirements of this standard when used with any bulb of the type specified by the lamp manufacturer, operated at the bulb's design voltage. A lamp that contains a sealed-in bulb must meet these requirements with the bulb operated at the bulb's design voltage.

 

Just a sample in the definitions, need to READ all of this I can cite more in the body of the document. FWIW I deal in this stuff for a living CFR that is just different parts for 33 years lol.

"Effective light-emitting surface means that portion of a lamp that directs light to the photometric test pattern, and does not include transparent lenses, mounting hole bosses, reflex reflector area, beads or rims that may glow or produce small areas of increased intensity as a result of uncontrolled light from an area of 1⁄2 ° radius around a test point.

Effective projected luminous lens area means the area of the orthogonal projection of the effective light-emitting surface of a lamp on a plane perpendicular to a defined direction relative to the axis of reference. Unless otherwise specified, the direction is coincident with the axis of reference.

Exposed means material used in lenses or optical devices exposed to direct sunlight as installed on the vehicle.

Filament means that part of the light source or light emitting element(s), such as a resistive element, the excited portion of a specific mixture of gases under pressure, or any part of other energy conversion sources, that generates radiant energy which can be seen.

SMALL SAMPLE OF REQUIREMENT's---

"S10.18.9.1.5.1 The headlamp is mounted on a headlamp test fixture which simulates its actual design location on any vehicle for which the headlamp is intended. The fixture, with the headlamp installed, is attached to the goniometer table in such a way that the fixture alignment axes are coincident with the goniometer axes. The headlamp is energized at the specified test voltage. The cutoff parameter must be measured at a distance of 10 m from a photosensor with a 10 mm diameter.

S10.18.9.1.5.2 The headlamp beam pattern is aimed with the cutoff at the H-H axis. There is no adjustment, shimming, or modification of the horizontal axis of the headlamp or test fixture, unless the headlamp is equipped with a VHAD. In this case the VHAD is adjusted to zero.

S10.18.9.1.5.3 A vertical scan of the beam pattern is conducted for a headlamp with a left side gradient by aligning the goniometer on a vertical line at 2.5° L and scanning from 1.5° U to 1.5° D. For a headlamp with a right side gradient, a vertical scan of the beam pattern is conducted by aligning the goniometer on a vertical line at 2.0° R and scanning from 1.5° U to 1.5° D.'

 

Congrats, you cited the definitions section. That just states what terms mean in the rest of the document. Read further down the document where it tells you how to perform tests and what to look at.

 

 

I posted that part. To be frank here you are not exactly understanding the entire context of the document. READ the entire document along with the other ancillary specifications and testing methods cited and you will understand. I have made my point and provided the Federal Specifications for DOT for everyone to see.

Good Luck I have no more to add to this .