A new paper in Transport Reviews by Adam Millard-Ball and Lee Schipper asks Are We Reaching Peak Travel? Trends in Passenger Transport in Eight Industrialized Countries.
Ball and Schipper looked at data from 1970-2008 in the United States, Canada, Sweden, France, Germany, the United Kingdom, Japan and Australia. They show that increases in passenger activity have driven energy use in transport, because growths in activity have swamped increases in efficiency. But the relationship between travel and GDP changed during the last decade. Previously increases in GDP lead to increases in travel, but in the last decade travel seems to have plateaued, and this halting of growth does not appear to be due to increases in gas prices. This is shown in Figure 2 in their paper.
One of the challenges in planning for the future is anticipating inflection points in ongoing trends. This paper could have made this point stronger if they compared predicted vehicle use against actual vehicle use, but that was not their main point.
As with total travel activity, the recent decline in car and light truck use is difficult to attribute solely to higher fuel prices, as it is far in excess of what recent estimates of fuel price elasticities would suggest. For example, Hughes et al. (2006) estimate the short-run fuel price elasticity in the U.S. to range from -0.034 to -0.077, which corresponds to a reduction in fuel consumption by just over 1% in response to the 15% increase in gasoline prices between 2007 and 2008. In reality, per capita energy use for light-duty vehicles fell by 4.3% over this period.
…[in these countries transportation sector] the major factor behind increasing energy use and CO2 emissions since the 1970s – activity – has ceased its rise, at least for the time being. Should this plateau continue, it is possible that accelerated decline in the energy intensity of car travel, some shifts back to rail and bus modes, and at least somewhat less carbon per unit of energy might leave absolute levels of emissions in 2020 or 2030 lower than today.