Expert Commentary

Peak travel? Trends in passenger transport

2011 Stanford and U.C. Berkeley study on global trends in transportation and how they may impact predictions about future carbon emissions levels.

Travel demand and vehicle use rates have generally increased from the 1970s through the early 2000s. These trends often inform projections about global energy growth, increases in greenhouse gas emissions and climate change scenarios.

A 2011 study by researchers at Stanford and University of California, Berkeley, “Are We Reaching ‘Peak Travel’? Trends in Passenger Transport in Industrialized Countries,” provides analysis of transportation trends in six industrialized countries (Japan, Canada, Australia, Sweden, the Unites States and the United Kingdom). Their research suggests that less total travel per capita and shifts away from energy-intensive forms of travel could result in diminishing transportation energy consumption and, potentially, declining global greenhouse gas emissions.

The study finds that:

  • In the last three decades there were rapid increases in total travel activity, but since 2003 motorized travel demand by all modes has leveled out or declined in the majority of countries studied, and that travel in private vehicles has also declined.
  • Although car ownership has continued to rise in most places, it has been at a slower rate, and these cars are being driven less.
  • Overall total domestic travel across all six countries has slowed its growth relative to GDP and has declined in per-capita terms in some countries.
  • Current trends in increased transportation efficiency, stagnation in total per-capita travel, and lower rates of carbon generated per unit of energy could cause the absolute levels of emissions in 2020 or 2030 to be lower than current levels.

The study indicates that energy projection models that have predicted consistent rises in vehicle miles traveled are overstated. If global “peak travel” is being reached, the researchers suggest, this should be reflected in predictions about future global emissions levels.

Tags: cars, carbon, greenhouse gases, mass transit

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