> According to a document by SafeLite of America, Inc., that you enclosed, its product Safe-T-Stop "will pulse [the center high mounted brake light] for approximately 6 seconds and reactivate if the brakes are reapplied." You read S5.5.10(d) of Federal Motor Vehicle Safety Standard No. 108 as requiring "that the third brake light must be wired to be steady-burning," and that you believe that Safe-T-Stop "contravenes this requirement of the standard by varying the brightness of the light."
> We confirm your interpretation. S5.5.10(a), (b), and (c) list the motor vehicle lamps that may flash when they are operated. No stop lamp is among the lamps listed. S5.5.10(d) requires all other lamps to be wired to be steady burning, thus including all stop lamps. Standard No. 108 does not allow a stop lamp that pulses, and a vehicle with a stop lamp that pulses does not meet Federal requirements.
It's clear that there's not much enforcement, since all the dealers I've visited near me install these things by default. If you commit to a car that's not yet delivered, you can negotiate to exclude these, or you can have them remove it (but they'll most likely have cut into the factory harness to install it, so the wiring harness has been modified, which is a negative IMHO).
Personally, I find these devices to be pretty terrible. I would be fine with flashing for high intensity braking, but the flashing is attention grabbing by design, and it's inappropriate in a lot of situations as it distracts from gathering awareness of the surroundings.
No one cares, not all states have mandatory inspections, and many inspectors just check if the brake light comes on when they press the brake pedal which would not reveal such an aftermarket device.
The only way to catch something like this would be a road driving test by the inspector, and even here in Europe this is not required.
IIRC in the USA there are features allowed to be installed aftermarket that aren't legal to be installed as a dealer option (like front side-window tinting)
