While riding home from the LBS, I saw a bike whiz through a red light. I only caught a quick glimpse lasting a few seconds and couldn't figure out how the guy was turning the crank while the chain remained stationary. The bike had derailleurs from which the chain was sagging as with chain suck. I've been trying to solve the riddle. Maybe the chain had just dropped and the cranks were still turning? He was definitely accelerating and the cadence was even, not sudden overspin as when a chain drops. Maybe it was a left drive and the chain was hung from the derailleurs as an ornament? I never got a good look at the crankset to see if the chain was on the ring [that couldn't be] or hanging on the bb shell. I was too busy ogling the sagging chain from the rear derailleur as he was hammering and wondering what in the hell did I just see and how was that possible. Maybe the setup is his sense of humor for knocking road bikes, i.e. derailleurs are dead. Anyone who doesn't ride or build/service their own bikes would likely have ever noticed something was amiss. Why didn't I chase him down you ask? I just had right carpal tunnel release surgery last week and am riding essentially one handed. Yes, I flipped the wheel and am using a front brake to slow me down as I "coast" up to the stop lights. Post-op wasn't a good time to learn how to stop with only one hand on the bar. Best of luck with the riddle. Many thanks for helping me to solve it. Live well, ride your bike!