Originally Posted by mcmoose

I make no claim to be wise, but I'll toss out two possible smile-inducing aspects:

1) Mechanical Advantage -- bicycles are wonderful machines that magically increase the output of our physical efforts. There are a few elite humans who can run 15 mph... most of us can ride along at that speed (or much higher). There's an inherent pleasure in having that level of physical efficacy.

2) Near-Perfect Optic Flow Rate -- we are visual critters, and there's an intrinsic joy in watching the world flow by. But driving in a car is really too fast to appreciate the world around you (although there's another kind of fun in honing in on the road in a speeding car), and walking is too slow to be that visually interesting (unless you're surrounded by visual wonders). But biking -- that's pretty much a perfect pace.