Under the assumption that vehicle miles growth causes GDP growth, what are the possible explanations of that relationship? It seems to me this means that vehicle miles (or  perhaps passenger transport volume for the European case) must relate directly to some component of the economy that is "limiting" in the same sense that, in a chemical reaction, one molecule is often the "limiting reagent". That is, everything else is in relatively plentiful supply for the stoichiometry of the reaction, except for the limiting component, so the quantity of product of the reaction scales directly with the quantity of that limiting component, no matter how complicated the reaction and associations of all the other molecules involved.

It might be helpful to identify what this limiting component is by imagining a world where there were no limits on transportation; where we could go as far as we wanted within the world at any time, at any instant, "Star Trek transporter"-style, perhaps. We wouldn't use that facility mainly for transport of goods; goods go point to point, not back and forth, and as has been pointed out elsewhere, our dependence on physical material goods has been at least gradually declining.

What I imagine we would do with unlimited personal transportation is the equivalent of what we do on the internet now, but in person: inserting our specialized knowledge and skills where needed at any point in the world at any time, going out to gather in-person information about what's going on out there, participating in social events around the world. Rather than trying to communicate over the phone with colleagues in India having trouble getting our automated emails, I'd bop over there for 5 or 10 minutes and try to trace where exactly the problem is coming from. Rather than venturing out to the water park only once every couple of years, hoping the crowds aren't too bad and the weather's good when we get there hours after we depart, we'd probably buy a membership and enjoy our favorite spot almost every summer evening.

With instantaneous travel we could be far more productive, have far more leisure time, and take the economic benefits of the division of labor that globalization makes possible to the limit. So, perhaps present limits on personal travel are the "limiting reagent" in economic growth, at our present stage of world development?