In order to reduce dependence on imported oil, the government of Jalica has imposed minimum fuel-efficiency requirements on all new cars, beginning this year  The more fuel-efficient a car, the less pollution it produces per mile driven
As Jalicans replace their old cars with cars that meet the new requirements, annual pollution from car traffic is likely to decrease in Jalica
Jalicans who get cars that are more fuel-efficient tend to do more driving than before.