The absolute number of vehicles reached a maximum in 2008. However, it is likely that this was only a temporary maximum and that the decline after 2008 was primarily driven by the current economic downturn that started in 2008. Consequently, with the improving economy and the expected increase in the U.S. population, it is highly likely that (from a long-term perspective) the absolute number of vehicles has not yet peaked. On the other hand, the rates of vehicles per person, licensed driver, and household reached their maxima prior to the onset of the current economic downturn. Consequently, it is likely that the declines in these rates prior to the current economic downturn (i.e., prior to 2008) reflect other societal changes that influence the need for vehicles (e.g., increases in telecommuting and in the use of public transportation). Therefore, the recent maxima in these rates have better chances of being long-term peaks as well.
But Sivak is smart enough to hedge his prediction:
However, because the changes in the rates from 2008 on likely reflect both the relevant societal changes and the current economic downturn, whether the recent maxima in the rates will represent long-term peaks as well will be influenced by the extent to which the relevant societal changes turn out to be permanent.
There is a lot of worthwhile data in his new paper but if you are going to look at just one data picture, this is it:
Sivak has written many, many other interesting papers about U.S. transportation. Related: interesting Times article by Matt Flegenheimer about (NYC Mayor) Mike Bloomberg‘s efforts to fund and institute smart traffic ideas all over the world. I have to say, it is a nice thing to be a New Yorker these days and travel around the world now and then — because people always ask about this magical mayor with the good ideas who actually has the ability and courage to try them out. I have come to think of New York as the world’s biggest laboratory for forward-looking social improvements, and Bloomberg as the crafty scientist who’s running the shop. (You may think of him as simply a billionaire mayor with a Wall Street background, but in his youth he was an Eagle Scout and full-fledged science nerd.)