Two key inputs to the model are the total vehicle miles traveled (VMT) for light duty vehicles (LDVs) in the US over the 21st century and the annual number of new car sales.
VMT. While improved fuel economy with technologies such as hybrid vehicles can cut down air pollution and oil consumption per mile, if there are more cars on the road traveling farther each year, then pollution could get worse despite improved vehicle efficiency. Historically, VMT has been increasing steadily due to several factors:
- Increasing population
- Increasing percentage of cars per person
- Increasing miles traveled by each car
For this computer model, we use a linear extrapolation from the EIA’ Annual Energy Outlook (AEO) data for 2012 that projects VMT through 2035. As shown in this graph, the EIA’s annual projections of total VMTs have been trending downward. We use the lower AEO 2012 projection, meaning that the total miles traveled and therefore the pollution and oil consumption will be less for all vehicles than in our previous simulations that used the 2009 extrapolations.
LDV sales. As with VMT projections, the EIA has been decreasing their estimates of new car sales following the Great Recession of 2008-2009; again, we use the lower (2012) projections in this model: