Strobe effect on Cadillac brake lights?

[Ponch8]

In the past couple of years, I've noticed that the rear brake lights on Cadillacs (and no other makes of car) almost have a very rapid strobe-light effect. When I stare at the lights and then shift my eyes ever so slightly, it is very noticeable. Has anybody else noticed this?

[Squink]

LED's. Pulsed output.

[One Day Fish Sale]

I've noticed this too. The Cadillacs and other newer cars you're seeing use light-emitting diode (LED) tail/brake lights instead of standard incandescent bulbs. To control the brightness of the tail/brake lights (dim when acting as a tail light, but bright when braking), the LEDs must be switched on and off at somewhat-high frequency. This pulsing (pulse-width modulation, I think) causes the flicker you see.

Some people seem to be more sensitive to this than others. To me, it's distracting, and I wish they'd just light fewer LEDs for the tail light, rather than dimming all the LEDs in the array. I do like LEDs as brake lights in principle, since they come on instantly, and are more noticeable.

[Saintly Loser]

I've always run brake light flashers on my motorcycles (Hyper-Lites is the brand name). It's anecdotal, I know, but I'm pretty sure they've saved my ass a couple of times.

[GargoyleWB]

Yes, PWM was mentioned, it is a common technique to control the brightness of LEDs. I'm very sensitive to the flicker and I've come across many "cool and advanced" architectural lighting schemes that I can notice the flicker (despite claims of it being imperceptible) and often develop a headache from it. Peripheral vision is especially noticeable, which is why it really stands out with automobile applications.

It's unfortunately reminding me of the CRT refresh rate days and I'd thought I'd been able to say goodbye to those monitor-flicker-induced headaches