I've seen a few bikes recently with a pulsing tail light display, as contrasted with the more normal bright flash-pause-bright flash look. That is, the light never goes all of the way off.

Unfortunately, the riders with these lights were faster than me and I never caught up with them to ask which light they were using! I liked the residual "marker" effect of having a bit of light left on, plus the "I'm a bike in front of you" signature (at least here in the USA) that the flashing gives.

Any ideas which lights have this feature, or setting? I imagine that these are multi-LED taillights and one of the LEDs just stays on all the time, while the others flash.