I was so entranced--and I suppose I am that geeky--by Rebecca Wilder's vehicle miles traveled vs gasoline price graph proving that people in the US drive less when gasoline costs more that I drew up two new graphs of the change in vehicle miles traveled vs gasoline and diesel prices in real 2008 dollars from 1980 to October 2008.
These do make one expect, however, that no matter what people are telling Gallop, the low price environment should increase the number of vehicle miles driven. I suppose the limiting factor is the "once in a 100 years" financial event, which is hard to "price in" via data from 1980 on. Still, I'd imagine miles driven will go up, just not as much as a similar prices in the past would suggest.
You'll note that $2.50/gallon (for both diesel and gasoline) appears to be the breaking point.
Ms. Wilder is the muse of Microsoft Excel! =D
UPDATE: I graphed in 2008 dollar cost averages of crude imports against vehicle miles driven. It looks like the breaking point in terms of average imported crude costs (which account for about 50% of crude consumed in 1980 and 60% today) is a little over $70/b.
I tried plugging in average monthly price of front month sweet light crude on NYMEX in 2008 dollars to see if I could get a breaking point for the pricing mechanism itself, but the EIA data only goes back to 1983. Anyways, for your viewing pleasure:
I guess you might conclude that the breaking point might be somewhere around $70-75/b.