Peak Travel, or biological limits on techonology and growth

Saw this article at MR a few weeks about peak travel, and then this one at the Freakonomics blog more recently. It turns out (ahem, James) advanced economies seem to be reaching a peak of their per capita annual vehicle miles traveled.

It reminds me of talks with Kraft and Stan I had a while ago about the biological limitations humans place on technology. I pointed out that the human eye cannot tell the difference between anything at 60 frames per second and something higher. High definition 120hz televisions are the end of the line in 2-D visual advances because humans simply *cannot* tell the difference between that and anything better. So instead of upping televisions to 600hz (which is no different from 120hz, for all intensive purposes), televisions will go 3-D, get bigger, and get thinner. That's about it.

Similarly, humans only get to work with 24 hours in a day, and most of us need > 5 hours of sleep a night. We can only travel for so many hours a day, although we can increase the speed at which we travel, affecting the number of miles we travel. But it makes sense to me that people in an advanced economy would eventually achieve a certain number of leisure hours and use them to travel. Fixing the method of travel (or assigning an elasticity of 0 < e < .1 for advances) means the marginal benefit of more leisure time on travel will decrease immensely.

Using John Holland's building blocks theory from complex adaptive systems, I would predict that we haven't reached peak travel yet. We know what our building blocks are, and we've rearranged them into a pretty optimal arrangement. We'll hover where we at number of miles traveled until we introduce something new to the equation that allows us to advance by leaps and bounds. For a humorous example, think flying cars The Jetsons style: It's a new building block that would vastly increase the number of miles people travel.

Here's another limitation, although it has to do with general physical limitations: we keep building better and better computers. I've been reading about people storing immense data in bacteria, or computers being made at the atomic level. My question is, can we go any smaller? Once we master pushing around atoms to do computations, is there anything lower? Quantum computers? What then? Have we hit that limit?

Can we predict any other biological limitations?