[flimflamm]

Imagine your eye's effective integration time (the period over which it "samples" light) shrinks during a rapid saccade—say down to about 5–10 ms. Under steady conditions, our flicker fusion threshold is around 60 Hz, but that’s because our retina integrates over a longer window.

If we want to “smooth out” the PWM cycles so we don’t see discrete pulses, we need a few cycles (say, 3–5) within that 5–10 ms window. In other words:

    For a 10 ms integration window:
        3 cycles → f≥30.01 s=300 Hzf≥0.01s3 =300Hz
        5 cycles → f≥50.01 s=500 Hzf≥0.01s5 =500Hz
    For a 5 ms window:
        3 cycles → f≥30.005 s=600 Hzf≥0.005s3 =600Hz
        5 cycles → f≥50.005 s=1000 Hzf≥0.005s5 =1000Hz

So, to cover worst-case scenarios (rapid eye movement, bright conditions where the eye’s temporal resolution is higher), the PWM systems for LED lights should be rather in the ballpark of 300–1000 Hz than 200 Hz. Given that one would be viewing headlights some 2 meters away (impacts the what is the view angle change and speed).

And yes, what we are now seeing in cars is super annoying. Similar disregardful to user comfort can be seen with HUD displays (at least with Volvo).