To make things clear, the term "DOT approved" is a misnomer; meaning that the phrase we all think we know does not actually mean what it says. Let me clarify...
According to the Department of Transportation's (DOT) National Highway Traffic Safety Administration (NHTSA):
"DOT does not approve any motor vehicles or motor vehicle equipment items as complying with all applicable FMVSS (Federal Motor Vehicle Safety Standards ). That is instead the responsibility of the vehicle or equipment item's original manufacturer." 
In other words, the DOT does not approve anything.
The DOT does however list 13 items that they list as "regulated" motor vehicle parts including: tires, rims, brake hoses, brake fluid, seat belt assemblies, lighting equipment, glazing, motorcycle helmets, child restraints, compressed natural gas containers, rear impact guards for trailers, platform lift systems for the mobility-impaired, and triangular reflective warning devices - but again, these are not "DOT approved" items!
What if the item has a DOT symbol on it?
On regulated items, the manufacturer places a "DOT" logo on it to state that it meets all of the regulations set forth by the DOT. This is simply the manufacturer claiming that it meets the DOT standard.
But, my headlights say "DOT Approved"?!
Any claim as "DOT approved" by the manufacturer is not true. They are simply using the confusing marketing word that is widely accepted by society. Headlights with "DOT" stamped on them are simply stating that they (the manufacturer) meet the DOT (FMVSS) Standard 108 (571.108) for vehicle lamps.
So, the F.R.E.D. Light and Michelin High Visibility LED Road Flares are not DOT approved?
Correct. There is no way that the F.R.E.D. Flare, Michelin Flare, or any other device to be DOT approved. However, our device does meet the regulations set forth by the DOT and is DOT Compliant under 49CFR § 392.25 & 393.95(g).
What does DOT Compliant mean?
This phrase is not a legal term, but for us it means that our device meets or exceeds the standards set by the DOT for such devices.
What is "49CFR § 392.25 & 393.95(g)"?
This is the DOT FMCSA code for "Emergency Equipment".
> §392.25 Flame producing devices:
No driver shall use or permit the use of any flame-producing emergency signal for protecting any commercial motor vehicle transporting Division 1.1, Division 1.2, or Division 1.3 explosives; any cargo tank motor vehicle used for the transportation of any Class 3 or Division 2.1, whether loaded or empty; or any commercial motor vehicle using compressed gas as a motor fuel. In lieu thereof, emergency reflective triangles, red electric lanterns, or red emergency reflectors shall be used, the placement of which shall be in the same manner as prescribed in §392.22(b).
> §393.95(g): Emergency equipment on all power units.
Each truck, truck tractor, and bus (except those towed in driveaway-towaway operations) must be equipped as follows:(g) Restrictions on the use of flame-producing devices. Liquid-burning flares, fusees, oil lanterns, or any signal produced by a flame shall not be carried on any commercial motor vehicle transporting Division 1.1, 1.2, 1.3 (explosives) hazardous materials; any cargo tank motor vehicle used for the transportation of Division 2.1 (flammable gas) or Class 3 (flammable liquid) hazardous materials whether loaded or empty; or any commercial motor vehicle using compressed gas as a motor fuel.
*This blog is solely intended as an informative reference material and is not legally binding nor is it to be used as definitive legal advice; it is an opinion piece based upon the standards set by the NHTSA and other governing entities. This content is not endorsed or approved by the NHTSA or any other agency... In other words, this blog is not DOT Approved.