In-A-Gadda-Da-Vida (the full 17:05 album version) started playing on the stereo, via my old iPod. I wasn't driving far, so I wondered whether I'd arrive before the song finished. I arrived just as the last couple of measures were playing. My destination had been one In-A-Gadda-Da-Vida (or IAGDV) away.
Not only is the IAGDV a handy unit of measure, it's a somewhat entertaining one. If you were around in 1968, you could reminisce as you drive—unless the drugs erased part of your memory. You could drum along on the steering wheel. You could sing the organ solo. And before you knew it, you'd be at your destination. Or it would be time to hit the replay button and keep driving.
True, there are longer rock & roll songs, and cases could be made for them being units of travel. But except for part of "Shine on You Crazy Diamond" (which is way too mellow to be driving to) I don't have them on my iPod. So there. Bomp bomp ba-da-da BOMP!